I will be sticking with 3.5 for the time being until the dust settles a bit. I'm not virulently anti-4e, but I don't really see any compelling reason to upgrade at this point.
When 3e came out, there was a broad consensus that it was time for a new edition. 2e was increasingly broken due to the proliferation of seriously unbalanced kits. Although 3.5 has its fair share of problems, I just don't see the same kind of consensus that it's time for a new edition emerging at the moment.
Frankly, I'm fairly ambivalent about most of the information released about 4e so far. I do like some of the mechanical changes that are being promised, but I dislike others. I can probably house rule those things that I don't like, I don't see why I should go to the trouble of customizing the game to my own taste unless there is going to be a decent payoff.
At the moment, most of my concerns about the direction that 4e is heading in are more about the fluff than the crunch. I am alarmed at some of the radical changes to the D&D cosmology that have been announced. And I am even more alarmed at the radical changes to the standard lineup of races. These things make it very hard to migrate an existing 3.5 campaign to 4e. Furthermore, IMHO the function of the core rulebooks should be to provide the tools for to run a generic 'Gygaxian' fantasy setting. By all means, add exotic options in later supplements for those peole who want them. But retain the classic 'feel' of D&D in the core rules.
To be quite honest, perhaps the biggest barrier for me is the size of my existing investment in 3.5. I'm very disappointed that there is to be no backward compatibility between editions. 4e will really need to rock my world before I rush out and buy all of the same material all over again, and at the moment I am not convinced that it will.
