David Hobby over at Strobist has given the Nikon SB-900 a good run-through and shares his thoughts on the new $500 speedlight.
One other noteworthy change is that the SB-900 swings both ways — you can go reverse 180 in either direction. This is especially useful, in that whichever way you mount a remote flash you can have the receiving window facing the master light source.
Jump on over there to see whether you should sell all of your SB-800’s to make room in your bag for SB-900’s. (Ok, it’s not that simple, but David’s got some great insights on the pros and cons of the new flash, particularly for those of you who already own a stable of SB-800’s.)