I am not sure what features the 550D has for remote TTL flash control but I assume it will have something. I would assume the TTL will still work to the flash units and the big bonus I see is the ability to wake the flash up remotely without having to walk over to the flash. That really annoyed me with my cactus units. THe cactus remote wireless trigger are great value and work flawlessly and would be ideal for more static type shoots where manual falsh control settings are relatively static. But I find the need for TTL with manual remote control of the flash as is offered with these new unitsl Very interested to see what you think if you do purchase. They are extremely well priced for fuller featured TTL enabled units.