Speaking as a game designer who knows the system pretty well (and a lot of the background of why things were done a certain way), I think that some of the 3.5 changes are good and were needed, and I think some are serious mistakes.
Speaking as a publisher, 3.5 scares me. Not as much as it did when it was being worked on a while back, but still somewhat. (If the changes had been larger and more invasive, it would have had the potential to cut the audience right down the middle.) It scares me because all it accomplishes is it makes the straightforward D&D audience (from which I pull my % of customers, just like most every d20 publisher) smaller.
By "straightforward D&D audience" I mean people who understand what you mean when you say "power attack" or "huge greatsword." The common man gamer, so to speak. It means I have to choose, as a publisher, whether my books will support one group of gamers rather than another, when for the last three years, there's just been one group.
Sure, I think most people will switch to 3.5. But does most mean 90% or does it mean 75%? We don't know yet and I don't know of anyone in the industry today savvy enough to really know that answer ahead of time. That's kinda scary. And even if it's 90% (which I think is the farandaway, outside, very best case scenario), why would I be happy about my potential group of customers being cut to 90% of what it was?
I plan on doing an extensive review and commentary on 3.5 when it comes out and my NDA goes away.