I will be updating to 3.5, but I'll be keeping my 3.0 Player's Handbook.
However, I will not be buying the miniatures, and I will not update to 4.0 when it comes out.
I think it was Buttercup who said earlier in this thread that she has enough 3.0 material to last forever.
I'm in the same boat.
With all of the d20 companies offering 3.0 and 3.5 material (something that did not happen with 1E and 2E), I see no reason to go beyond 3.5 (which is about as much revision as I want to tolerate, sans miniatures).