I got my hands on a 645DF today and had about 30 mins to play with it.
First impression, AF is alot faster than the AFDIII model i noticed it right away. The shutter button is alot smoother more like a dslr, i like it alot. And the shutterlag is impressive, alot faster then previous model. The grips is also changed a bit which is an improvement.
Didn't test image quality on the 80mm lens. The 110mm which i'm interested in will be available in january and is said to be extremly sharp
The grip will be available in april and have some cool functions. My rep gave me some clues that there will be a possibility with more functions on the grip which sounds great
I've already ordered my upgrade and will probably get the 110mm to but that will expensive probably same price as the 150mm 2.8D i think
1/1600 flash sync on the LS lenses will only be available on p40+ and p65+ for the other backs only 1/800.