Consider me a sceptic. I am worried Pathfinder is changing too much just for change's sake, and doesn't solve the real problem of 3.xE: that the game gets horrendously complicated at high level.
Races: why any changes at all? While I am sure it's easy to bring up complaints about this race being too strong here and that race being too weak here, were the 3.xE races
truly broken? No, they weren't. And I believe the benefit of staying 100% compatible with 3.xE would outweigh any benefit from changing them around, forcing us to learn a new ruleset.
Classes: "Cleaning up" isn't what a fix should be about. If there were any broken features (and there were) those should be fixed, and that's it. Saying "Our Pathfinder Fighter is better than the 3.xE Fighter" is just introducing power-creep right then and there. Not all games use the full plethora of splat-books. Fixing Druid's Wild Shape, on the other hand, is a real need.
Spells: Both fixing individual spells and getting rid of Save-or-Die sound good!
Assuming the changes are fully integrated into the text, this is the kind of change we're looking for!
Regarding spells: one of the major headaches of high-level 3E play is the multitudes of spell effects, all with different durations. Is this (possibly the most crucial) aspect of the game changed (so you don't have to count rounds for a dozen spells simultaneously)?
Combat: If I understand you correctly, Pathfinder will attempt to unify certain maneuvers. Correct? If so, great. As long as the game only changes for aspects that caused trouble, that is. Changing grapple would be wonderful; messing with BAB or iterative attacks would be disastrous.
Magic Items: okay, so I'll wait on this one. Of course, unless the change really trims the Christmas tree, it should not be made at all.
No XP costs. Again, I'm not sure I understand what was broken to such an extent, a "fundamental" change was needed. Are you sure this isn't just designers wanting to put their mark on the fix, thus breaking compatibility...?
Skills: I read that other thread, but came away confused. Not a good sign the change is really worth it. I must say, the 4E skill approach is sufficiently effective at reducing clutter to be worth it. I sincerely hope Pathfinder isn't just a conservative messing about that only accomplishes incompatibility while still not making things so much more easy it's worth the switch...
In summary, I fear Pathfinder will be as compatible to 3.5E as 3.5E was to 3.0E. Which is to say, not very compatible at all.
I fear that when Pathfinder finally becomes available, the moment has passed. Everyone will by then be playing some other game. And those still running 3.xE campaigns? Well, one thing they won't be interested in, is having to make yet another conversion where everything changed but still all remained as before.
But I could be wrong.
Regards, Zapp