These suckers are finally in hand. I ordered them about two and a half weeks ago while they were on sale at Adorama. The kit included 2 600EX-RT Flash units along with a ST-E3-RT transmitter. For about 2.5 weeks the transmitter was back-ordered and I could not receive the kit. I decided to call Adorama and ask if I could pick up the heads and come back later for the transmitter. They agreed!
I’ve briefly tested these guys out, customized them through the personal/custom functions, and now have to buy rechargeable batteries for them. I’ve had the Canon 580EX II since June 2012 (almost 2 years) and it has been very reliable. The 600EX-RT’s main advantage is its radio transmission and extended zoom range (200mm). I also find the dot matrix display very easy to use; no more guessing when setting custom functions!
I plan to use these lights in the near future, and I’ll post a full review of them once I receive the ST-E3-RT transmitter.