I'm probably going to get alot of miscellaneous vegetables thrown my way, but I actually like alot of the controversial spell revisions.
Haste - this spell was way too powerful in 3.0. Having frequently played spellcasters I can say that this spell made more of a difference in my battle performance than any of my high level spells did. Yeah, it is less useful to spellcasters now, but I don't think most people realise that the 3.5 version is actually almost identical to the 2nd edition version of the spell. One can always design the 3.0 Haste spell as "Improved Haste" at 6th level, if they miss the old chessy, munchkin, who needs quicken, extravaganza of 3.0.
Invisibility spells I also like the change to these spells. It was way too easy for a Wizard to go around for hours doing the Rogue's job better than the Rogue could. These spells have seen alot of use by my current Wizard character and I actually like the suspense of knowing that they can run out.
Buff spells I have mixed feelings on the Bull's Strength and similar buff spells. For one thing, I always pictured spells that make creatures stronger, faster, etc not lasting for hours at a time. These spells never saw much use anyway in my games since most people would get items to enhance their attributes. I would think that adding a +2 hit and damage (from str) for 1 minute/level is probably about what a second level spell should be. Even at low levels it should easily last throughout an entire battle, and likewise lasts long enough that you don't have to worry about it running out quickly if you cast it in preparation of a battle. The ability to empower them was never much of a big deal to me. 1d4 + 3d2 +1 to an attribute as an 8th level spell is anything but overpowered. Oh well, just design higher level versions that give a higher bonus or last longer if you don't think the 2nd level spells are sufficient. They are only 2nd level, after all.
Scrying Another one I like. I thought that the ability to pretty much automatically scry on someone and there be little to nothing they can do about it was extremely cheap in 3.0. And thank god we no longer have the Scry skill!
Polymorph I like the changes here. Maybe the duration is a bit short, but I like how they divided the helpful and harmful versions of the spell in 3.5.
Scorching Ray Finally, a 2nd level alternative to Melf's Acid Arrow. My DM thinks this spell is overpowered. I totally disagree. Melf's Acid Arrow does less damage overall, but it only requires one attack roll to hit and is an excellent way for screwing up spellcasters throughout a battle. The 3rd level spells can do 10d6 to many creatures, so I dont think the ability to shoot three 4d6 rays is overpowered for 2nd level at all.
Hold Spells I like the change here. In 3.0 succesfully casting a Hold spell on someone meant the battle was over. Might as well have been an instant kill spell.
Sorcerer spell swapping Thank you, WOTC!
Now for the ones I don't like:
Spell Save DCs They went way too far, IMHO, in their efforts to "balance" save DCs. Even in 3.0 it was almost impossible for a spellcaster to keep up in Epic levels. Now I am simply uninterested in ever playing an Epic game because I know my spellcaster will be almost worthless.
Spider Climb This is one I don't like. I simply don't know what was on the developer's minds when they did this. Perhaps they neglected to notice the Levitate spell at 2nd level? A least now you can use the spell while wearing shoes though...
Daze Monster I don't get this. How is this worth more than a 0th level spell? I'll use Color Spray, thanks.
Polar Ray I am totally confused by this one. 20d6 dmg as a ray to one creature. And this is worth an 8th level spell?! Look at delayed blast fireball, a 7th level spell. No touch attack, up to 20d6 dmg, and it can hit many creatures at once. I can do 12d6 with the 2nd level Scorching Ray spell for crying out loud! This should be, at the most, a 5th level spell.
Sleep There is an entire thread on this topic. No need to go over it all again. I must say, though, it was still pretty worthless in 3.0. All they did by nerfing it was kick an already dead horse.
Ray of Enfeeblement People complain way too much about how Magic Missile is the overpowewred 1st level spell. They must have passed by Ray of Enfeeblement. This spell definately needs to have a savign throw.
Phantasmal killer I can't believe they didn't change this spell. An instant kill spell is way too powerful at 4th level, even if it does allow two saving throws. For that matter I hope desperately that they change the Druid spells Miasma and Languor when Complete Divine comes out. If they don't, I can guarantee those spells will be banned in any game I DM!