Similarly, the 7D firmware upgrade does not allow the 600-EX RT to have a fast (1/250) shutter sync speed in Radio mode - you only get 1/125. I got confirmation of this from Canon today. I wonder what the technical reason is. If this worked, I'd upgrade my 2 580EX II's and 430EX to all 600 EX-RT's. I have one 600EX-RT already, and it's a nice unit.