For existing campaigns, we will debate and work it out. (I assume that's what the focus of this poll is.)
For new campaigns, the DM proposes the idea, same as if we were playing Mutants and Masterminds, or if we were playing another game system.
I think our gaming group, based on recent conversations, is likely going to go 3.5 all the way. We're suckers for new rules, after all. Then we'll come up with our own decisions for house rules. But it does make it so much easier when a DM doesn't have to hand out 5 or 6 pages of his own stuff when a new game starts.