Mostly 3.0 with the Haste, Harm, Heal from 3.5.
We also added a few things that helped color: Druid spontaneously casting Summon Nature's Ally, spontaneous spellcaster spell replacement, staff now uses better of its caster level and attribute or the users, that sort of thing.
For the most part, ignored the feat changes. Did go to +3 for skill focus, don't have to choose weapon for finesse, but that is about it.
In our group, 3.5 would have sold a *lot* better if they hadn't done as many changes. Adopting it wholesale would have been disruptive to the campaign, required reviewing the spells with a fine tooth comb, and then trying to remember all of the changes when they came up in game.