Class-wise, I'm of mixed feelings. I don't mind the 21+ progressions, or the bonus feats really. I think the seperate BAB and Save progressions are kind of dumb though. It'd be much simpler to just rule that you can't have more than four attacks (0/-5/-10/-15) and let BAB rise as normal. Saves, one of the major benefits of multiclassing is to cover your weaknesses, and there's certainly no shortage of feats, items, and spells to do that.
I'm not a huge fan of the spell seeds as they are now. I think I would have prefered the concept of spell seeds and had them take that and explain how to make spells of any level, but specifically 10th+. It just makes little sense to me to have a Vancian system at one point and a Skill-based one at another. On the other hand, I like the idea of only having 10+ spell levels be for metamagicked spells. I think I would have preferred a combination of spell seeds as I described above, and then metamagic feats which are more epic - Vast Spell as Plane Sailing described would be a good one.
The Fig/Wiz 20/20 versus Wiz/Fig 20/20 paradox definitely needs to be addressed. In my mind, these two should be equal, and they aren't under the current rules.