I have been having problems with my Sb-800 and 600 set up. No matter how much compensation I dial in everything comes out under exposed. I can remove umbrellas and point them at my subject from 5 feet and they still under expose. If I just set one flash on iTTL it does fine, so it is not a power issue. I use a TTL cord to place my master 800 off camera and then use it to control the 600. My other problem is that some times in the middle of a shoot the hole system just stops working. I get pre flashes, but the flash does not fire during the shutter. I get solid black no flash pics. After searching the net I find other people talking about this under exposure problem as well. Does the system just suck? should I just give up on TTL and go all manual. I was really hoping to avoid this because of speed and ease.