There are ten 7th-level cleric spells in AD&D (down from the 11 that were in OD&D). Nine of those spells were previously in OD&D: Astral Spell, Control Weather, Earthquake, Holy Word, Restoration, Symbol, Wind Walk and Resurrection (previously known as Raise Dead Fully). Aerial Servant and Part Water were 7th-level spells in OD&D, but in AD&D have both been dropped to level 6. The sole new spell is Regenerate (which sucks for me, because it's a lot easier to write the entries for new spells than preexisting ones).
Astral Spell: This spell allows the caster and up to five others to enter the Astral Plane, and from there to journey to the first level of any of the Outer Planes. (It can also be used to explore the material plane.) An astral character leaves their body behind, and is connected to it by a silver cord; if that silver cord is somehow severed, both astral and physical forms are killed. The most common occurrence that can sever the cord is the "psychic wind" of the Astral Plane - all of this stuff was previously introduced in the rules for psionics in Supplement III: Eldritch Wizardry, and it's cool to see it carried forward into later editions.
This spell also plays with ideas that Gary had previously introduced in earlier articles about the Planes. For example, only certain magic items which have a multi-planar existence can be taken along by an astral character: magic swords in particular were posited by Gary as existing in multiple planes. The Prime Material Plane is said to contain "the entire universe and all of its parallels". It's all consistent with the articles from The Dragon, and is expanded later in the appendix.
The major difference between the AD&D and OD&D versions of the spell is that this one actually explains what the hell it does. In OD&D, the spell was said to "allow the user to send his astral form from his body to other places". I suppose it was intended at that point to allow exploration without being detected, as no mention of the Planes was made (most probably because the D&D conception of the Planes had yet to be introduced). Most of the rest of the spell description was devoted to the chance that spells cast while in astral form would fail, and result in the caster being forcibly returned to his physical body, a factor not present in AD&D.
Control Weather: A spell to control the weather, obviously, which sounds powerful on the surface. I'm not so sure, though; as written, there are three factors that can be altered: cloud cover, temperature and wind. The caster can change the weather one step away from the prevailing conditions. So while the spell can't turn a heat wave into a sudden blizzard, it can lower the temperature to warm. A light wind can be calmed, or turned into a strong wind, and so on. For a 7th level spell, I'd expect something more dramatic. The weather effects don't even come into play straight away: the spell takes a turn to cast, then another 1d4 turns to take effect. That's around half an hour, give or take. It seems weak, but I feel like I'm missing something having never seen the spell in practice.
(Also, the practical effects of these weather conditions aren't given here, or elsewhere in the PHB. I'm all for DMs coming up with this stuff on the fly, but there should be some sort of rules framework to go on. So far, AD&D doesn't provide that.)
The OD&D version of the spell simply gave a list of effects that the spell could achieve, with things such as Rain, Heat Wave and Tornado. None of these effects were determined by the prevailing weather, they could just seemingly be created as the caster desired. If anything, this version of the spell seems over-powered, and I wonder if Gary overcompensated in the other direction when updating this for AD&D.
Earthquake: Creates a sudden tremor that affects an area of 5 feet per caster level. Everything within the area is affected: caves and tunnels collapse, buildings sustain damage, and creatures of less than Large size may be swallowed by cracks in the ground and killed instantly. This is much more in line with what I'd expect from a spell of this level. If anything, it's too strong: there's the potential for killing high-level characters with a single die roll that doesn't sit well with me. Actually, it's not dying to a single die roll that bothers me, it's that the die roll is has nothing to do with the character's capabilities. I have no problem with save-or-die effects, but that's not what this is. This is an area effect, and every Medium-sized character in that area has a straight, unmodified 1-in-6 chance of death. Small characters have a 1-in-4 chance of death. I feel like any die roll that can kill or injure a character should interact with their stats on some level.
The OD&D version was similar, but didn't factor size in when determining which creatures are killed. That spell specified creatures and left it at that, which sounds all kinds of over-powered.
Gate: The caster specifies the name of a demon or deity, and said demon or deity will step through a portal to aid the caster. Well, something will step through: the spell always works, but there's no guarantee that the correct entity will answer the summons. This is another spell that requires further information, presumably to come in the Dungeon Masters Guide. (I would think Supplement IV would come in handy here as well.)
The OD&D version was broadly similar, but it's hard to pinpoint exactly how this spell differed, because the percentages of success aren't given in AD&D. OD&D is much more specific about what kinds of entities can be summoned: it name-checks Odin, Crom, Set, Cthulhu, and the Shining One (which I'm not familiar with, but is apparently from The Moon Pool by A. Merritt). There's something to be said for the flavour gained from specific examples, but AD&D doesn't wear its influences quite so openly as OD&D did.
Holy Word: This spell is cast by uttering a word of power. Said word banishes evil otherplanar creatures to their home plane. The next sentence says that "it further affects other creatures of differing alignment as follows". I find this unclear: does it mean creatures of differing alignment to the cleric, or differing alignment to the aforementioned evil creatures? The OD&D version of the spell seems to affect everyone regardless of alignment, so I guess it's the latter.
As for effect, it kills creatures of less than 4 Hit Dice, paralyzes creatures of 4 to 7 HD, stuns those of 8 to 11 HD, and deafens those of over 12 HD. All this with no saving throw, I might add. Potent stuff. It can also be reversed as Unholy Word, which allows it to banish good otherplanar creatures.
Regenerate: This is the only new 7th-level cleric spell in AD&D. The spell regrows lost body parts such as limbs and organs, and will even regrow heads for creatures that have more than one. The process goes quicker if the original part is there to be reattached, but it's not a necessity.
The spell can be reversed as Wither, which is one I had forgotten about. It requires a touch attack, and will cause the touched "member or organ" (Gary's words, not mine) to stop working and shrivel away to dust. Once again, there's no saving throw: just as in OD&D, this seems to a standard thing for the highest level of cleric spells.
Restoration: Simply put, this is a spell to reverse level drain. It's not a perfect restoration, as it only raises your XP to the minimum needed for the lost level, but it's better than nothing. It can be reversed as energy drain, which replicates the level-draining capabilities of a wight.
The OD&D version of the spell was similar, but it didn't mention any rules for restoring lost XP. It also had a cost in that the caster would be incapacitated for 2-20 days, and it was specifically stated that this made it difficult to find NPC clerics willing to cast it. (Gary giveth, and Gary taketh also.) That penalty seems to have been taken out in AD&D, but it's added a restriction not present in OD&D: a requirement that the spell be cast within a certain amount of time to be effective.
Resurrection: This spell was formerly known as Raise Dead Fully, and the new name is a vast improvement. As before it's a spell to restore the dead to life, but unlike Raise Dead it also restores the target to full hit points. This spell refers back to Raise Dead for limitations on what types of creatures can be brought back, so it look as though elves are still out of luck. The caster must have a day of complete rest for every level of the creature resurrected.
The reverse of the spell is Destruction, which requires a touch attack and instantly turns the victim to dust. No saving throw, again. High-level clerics are a nightmare.
The OD&D version of the spell functioned much the same way, but no mention was made of the cleric having to rest after, and there was no explicit time limit on who could be raised (AD&D gives a limit of 10 years per caster level, which is plenty generous).
Symbol: The cleric inscribes a symbol in the air or on a surface. There are three symbols to choose from: hopelessness, which causes enemies to flee or surrender; pain, which penalises attack rolls and Dexterity; and persuasion, which alters the alignment of foes and makes them friendly to the caster. So far, this is the only 7th-level spell that allows the victim a saving throw.
The OD&D spell was similar, but had double the number of symbols to choose from. None of these symbols match the ones in AD&D, so the AD&D version is effectively an entirely new spell.
Wind Walk: This spell turns the caster (and others, depending on caster level) into a gaseous cloud that is blown around by a magical wind. It's good for escaping, scouting, and other stealthy activities, but it does seem a touch under-powered for its level.
The OD&D version was much the same, but the magic wind propelled characters a little more slowly. It also had a maximum limit of one passenger, whereas in AD&D the caster is able to take more allies at higher levels.
And that's it for cleric spells in AD&D. There wasn't much in the way of new lore, or tidbits to be picked up on, but what I'm finding with AD&D is that it's less about introducing new elements and more about consolidating what was already out there. Next up is the druid spell list, which ought to go by a bit more quickly, and then the magic-user spell list, which is going to be a slog. There's definitely more in the way of interesting bits and bobs to glean, though, so it'll be worth going through.