I really like 3.5e.
I'm not worried about it not being backwards-compatible.
I'm a programmer. I hate backwards-compatibility. The idea that it's preferable to create an inferior product just to cater to someone's perception of how easy the change-over will be is just wrong.
Now, the change-over should be made easy. It should be clear what has been kept and what has been changed. But "Backwards Compatible" engineering forces too many compromises, and engenders too much complexity -- which leads to too many opportunities for mistakes.
"Are these classes now all balanced within the new rules? Okay, good, now this week we're going to re-write them so they're also balanced under the old rules! Oh, and they have to stay balanced under the new rules the whole time."
Keep it simple, sophonts!
-- Nifft