First off I am not bashing Yongnuo, in fact I applaud Yongnuo and all they have done in bringing the Canon Wireless RT system to the masses, at a reasonable price and for correcting many of the omissions that Canon over-looked in developing this innovative flash system. It has been nearly 3 years since Canon introduced the 600EX-RT and the Wireless RT system and I would have thought by now, in fact I would have put money on it, that someone could have developed a receiver to work with the Wireless RT system sooner than this. I guess I was wrong and a good thing I did not bet that money but seriously, what took so long? Why didn't Canon step up and support their products and their faithful customers? Canons answer was to include the ability of the 600EX-RT to operate as a Master or Slave in the Wireless Optical system...What? That is backwards, backwards compatibility! Who wants to use a $600 RT compatible Speedlite in the Wireless Optical world? My hat is off to Yongnuo for developing this simple and ingenious little device!
Elvis did a great write up on these over at Flash Havoc last month ( http://flashhavoc.com ...ne3-rx-receiver-released/ ) so I do not have much to add to that other than to say that I picked up a couple and have tested them with a 580EX II, 320EX and Mitros+ flashes and they have worked just fine. A very simple device that addresses one of the first questions that a lot of people had about the Canon Wireless RT system and backwards compatibility with older EX Speedlites and the ability to use studio and non Canon shoe flashes with the Wireless RT system. If you want the redundancy of a radio wireless system to use with your older EX Speedlites then pick up a Yongnuo YN-E3-RT transmitter and a YNE3-RX receiver for each of your EX Speedlites and other non Canon flashes.