I've been checking out the PocketWizard MiniTT1 with the aim of increasing efficiency when using HSS on 580ex & 580exII. Also, does the 600ex-RT do HSS in an efficient way as offered by the PocketWizard MiniTT1?
Yes, the 600EX-RT does HSS.
IF you are considering the PW MiniTT1 and Flex system, you may want to check out the Phottix Odins - I have been hearing a lot of good things about them over at Strobist.com. Here is a review on them:
Interesting, it looks like a good system. But it's the power usage efficiencies that the PocketWizard MiniTT1 promises, with the associated ability to do an HSS burst. Regular HSS using big apertures & higher iso might deliver 2-3 frames in a 10 FPS speed burst. If the PocketWizard MiniTT1 savings could stretch this out by even a couple of frames it's valuable to me.