I got one on loan from Nikon for the Easter weekend. Really enthusiastic about it. Found out it can do about 12-14 high power pops equalling the D5 frame rate, with only 4 batteries. Radio trigger is really small, and can also be turned if you don't like it pointing upwards. The flash unit itself is slightly smaller than the SB-900 and weight point is lower than with previous speedlights. Build quality is more solid than with previous generation speedlights. Controls seem easy to learn and master, I still have not found use for the supplied manual.
Monday is scheduled for D5 and SB-5000 testing so drop a comment here if there is anything in particular you want to know.