I find it interesting how my feelings about the switch from 2nd to 3rd edition, and from 3.5 to 4th edition, are polar opposites.
When 3rd edition was announced, I was skeptical. I had fun with the game I had. Why change? Why buy a whole new set of books when the ones I had were still providing enjoyment? However, the more I heard about the changes that were being made, the more optimistic I became. Each issue of Dragon that introduced new concepts and elements allowed me to see how the game would be better with the changes that were instituted. By the time the PHB was about to be released, I was enthusiastic to see how the d20 system worked and what directions I could take it in.
However, with 4E on the horizon, I've seen nothing that makes me want to change editions. The changes either seem unintelligible to me, or they seem like something I could simply adopt as a houserule. I find it strange that many of the "problems" that people have with the current edition simply don't come up at my gaming table. I'm left scratching my head at the notion of abandoning tried and true classes and races from the core rules in favor of others, the terminology which seems like that which I hear from MMORPG players and "munchkins" than I do die-hard role-players...either the announcements of rule changes have been ambiguous and vague, or they've seemed trivial.
So I'm sticking with 3.5 (well, 3.25...not everything in 3.5 made sense to me either). I'll supplement my already considerable stock of gaming resources with the best I can find here at Paizo and from other d20 suppliers that have proven to have reliable product. I'll make a decent stockpile to draw from when I don't have time to create original material.
If it turns out, once all the 4E core books have been released and I've had time to read through them, that changing editions will be worth the money, time, and effort, then I may do so in the future. So far, nothing I've read or been shown gives me any real reason or desire to do so.