I have a grey set SB600 and a local warrantied SB800. Why? So far no problems with any flashes from cheap $35 Achievers to mid Vivitar 285HVs to SB600/800. Actually have, was firing in continuous mode and the Achiever stopped working. Switched off and on, couldn't clear the problem! Had to bring out another Achiever as backup (coz shooting wedding).... The first flash cooled and continued working. :sweat:
Looks like quite a no. of pple are asking about the SB600. Actually if you ask me, the SB600 is more than enough for a standalone TTL auto flash, even for single remote off-cam flashing. SB800 is useful with its faster flash cycling time (if you need it), modeling lamp to look out for shadow and highlight interaction on the face and the likes, and definitely is the one to get if you do multiple flash setup since you can control other iTTL flashes' output on the SB800 master (say for portraits and you don't want studio units which are bigger and not as portable). The extra flashes can serve as backup.
In short, SB800 is a bit too much to pay if you are not shooting much. (eg for leisure non-paid use), unless money is not a problem.
Don't have to follow him but this gives you an idea.
http://www.daveblackphotography.com/workshop/0407.htm