The books aren't for you.
Let me say that again, because it bears repeating.
The books aren't for you.
You're an enworld.org reader. The very fact that you're on this message board implies that you take a view of D&D "beyond the game", so to speak. If it were only about playing the game, then it would be as simple as looking over the changes in 3.5, taking what you like, ignoring what you don't, and going on your merry way.
But that's not you, and that's okay. Because the books aren't for you.
They're for the NEXT guy. The guy who walks into his FLGS and wants to play this D&D game that he's heard so much about. "Here you go", the FLGS guy will say, "D&D, 3.5. Newest edition, most up-to-date rules. These older supplements (pointing to all previous D20 supplements on the rack) will work with a few tweaks, but this (taps the 3.5 book) will cover all the new stuff."
And the new gamer says "Wow", because he finally gets to be a part of the game that we (that being you and I) enjoy.