It's an excellent trigger for 550EX
I have 3 550EX and 1 580EX for photo table setup with Harbor Digital Diffuser on each unit. This trigger works quite well with 1DS Mark-2 and flash setup I have. I don't have any AF cover fall off issue. And the hot shoe mount works quite good with a locking pin. It doesn't have a knob that you can tighten the unit on the camera but the unit is very light, and there's enough friction between the hot shoe and the trigger mount, so you don't really need to tighten it. I haven't tried long distance setup in the field as I use this for mostly product shot on the table. But it handles most indoor family gathering shots with no problem. It uses a special battery but it is readily available in many places where common batteries are sold. I always have an extra battery in the bag for just in case. This is an indispensable tool for my need and it is very reliable.
July 30, 2012
Looking for the next generation model
I've used this product for about a year now, and I have a complaint about how outdated this seems. I find myself using 580EX II's set to off for master flash work more than I use this. I am noticing that the only times I use this is when I need autofocus in low light conditions. It's not very cost effective for the price. The 580 EX II can do more than this can as a slave master and it's only a marginal cost more expensive. I hope that Canon updates this product, because it's useful, but appears to have become obsolete.
January 12, 2012
I had been happy with performance but now very disappointed in build quality. The AF filter came off while walking through a park. Unbelievable.
February 13, 2011
I've tried using this thing for a variety of different shoots, from portraits to action sports and it simply does not work well. The line of sight needed for it to work is frustrating. I love you Canon, but can we get a radio transmitter instead? For the price of this transmitter, save up a little extra and purchase two radio transmitters instead.
August 20, 2010