The clearest review of 3.5 that I’ve seen is here:
This release is like Microsoft charging for software updates. If you love the operating system and are devoted to it, you’ll buy it. If you’re a casual user, you’ll ignore it until a time comes when you need it, or have the means to get it. If you’re a first-time user, by all means, this is for you. If you prefer another operating system, it becomes moot. If you thought 3.0 and the D20 system was “broken”, a common euphemism for “these rules aren’t to my taste so let’s just hate them”, you’re not going to be impressed by 3.5, either.