The YN-E3-RT from Yongnuo is every bit as good, cost over a hundred dollars less and gives you Group mode with pre 2012 Canon cameras, and adjustable M mode in five groups with almost any camera make, even you Fuji owners, plus a very useful AF assist lamp. So far the only thing I have found the Yongnuo doesn't do is work properly in Remote Shooting Mode for pre 2012 cameras, it doesn't fire the flashes but does release the shutter. But considering the positives far outweigh that one minor negative it is tough to not highly recommend the Yongnuo YN-E3-RT over the Canon ST-E3-RT.
As an aside, I don't like the screen angle of either, if your camera is mounted on a tripod and tilted forwards a little it is very difficult or impossible to see the screen or work the controls, I much preffer the vertical screen of the 600's. Also the AF assist pattern of the YN is not as good as the 600 pattern and if you have a close working distance it gets ever higher in the frame, to the point that for product or macro work the beam pattern is out of the top of the frame.