I feel that many of the spells in 3.5 need to be redone, some in major ways.
With the way things are now whoever gets a round or two to prep is insanely good vs the other.
Now, of course those who have time should be better, but not to the point of literally shifting the whole CR system several points one way or the other.
I am all about much longer durations with weaker effects. This would mean that buffs are the norm, but most people have them to one degree or another, but their effects are more subtle.
The system already has in place safeguards about too much going on at once with named bonuses and stacking rules. So that safety net is there to help catch people.
Wizards and similar types are incredibly frail in a large number of ways, and so their effects should be stronger overall.
I feel that, if this is done correctly, it would help solve a lot of the more cumbersome balance problems that crop up now and then. Getting the jump on someone wouldnt be so incredibly one sided and there would be a lot more strategy involved with the sorts of buffs to put up and why.
Make it so that the maximum duration of a buff is 24 hours, even extend would not be able to break this, and there goes a good portion of the abuses.
As for other such spells, as much as I like the new haste I would have prefered they had both hastes in the new edition, but with the old haste simply clarified and reduced in armor bonus. After all, if they made sure everyone knew that the extra action only happened on your 'next' turn that helps get rid of a lot of the abuse, especially if that was its only benefit or the other benefits were very minor.
But again, this sort of spell places an emphasis on getting the jump on people, both versions do, but having a few spells here and there that do that is ok.
I have actually been seeing that the new version of haste is stronger than the old.. with the old there was a large amount of resource management problems, but the new gives everyone something that is basically free all at once. (of course, I also used the old haste as not granting the extra action right away as I feel that is more appropriate given the wording).
Longer durations with lesser effects. I am all about a buffer placing buffs on the party which last most/all of the day. Or at least a few hours at a time.