I'm currently running BB7s on my XC race bike. They are more than powerful enough for what I do but lately I've had the urge to upgrade to the Juicy 7s.
Honestly though...from a performance standpoint, I can't really see much difference in the BB7 vs the Juicy 7 once they are setup. I've ridden BB7s, Juicy 7s and Juicy 5s and they all feel about the same as far as power. The BB7s have slightly more effort on the levers but hey...I've raced V and canti brakes in the past so the BB7s feel lighter in that regard.
The real think I see is the Juicy brakes are self adjusting and sometimes it is a PITA to take off a wheel with the BB7s and then have to recenter the brakes or ocassionally have to adjust the pads.
Don't really see much weight benefit either.
I was looking at the 2008 Juicy 7s.