Hi guys
I just found the forum side of this site today. I've been using Sony 2500 mAh NiMH "AA"s for my 430EX and 540EZ with no problems. I'm shooting 8fps and I can get all 8 frames with flash most of the time. I carry 3 sets of 4 batteries including the ones in the flash. You might also find these useful:
http://www.countycomm.com/CBH.htm I just picked up 2 of them to keep my loose batteries under control.