Came from Nikon and have used the SB600 on a D90 for a few years. The only reason this product didn't get 5 stars is that Nikon's i-TTL way of working is truly the best in the interchangeable lens digital camera world. Just great. However, this flash is MUCH smaller than other "full" flashes, much easier to set up and use than the SB600 and. That's great. Once you set it up as an RC slave, it automatically knows when you put it on the camera that it wants to be in TTL-A mode. I want my Nikon to do this. This means that once set up it's very easy to just put it on, take it off and use it the way I want without having to mess with menus. The flash isn't as accurate as Nikon's, but it's really great. The reflectivity works well, the little built in diffuser and reflector work surprisingly well, but I'll probably add a Sto-Fen diffuser. The built in video LED works great and can be set to turn on automatically, but I still don't really like the video light so won't be using it very often. Finally, it balances VERY well on an OM-D camera (I have an EM-5, I'm sure it will work on the EM-1 and EM-10 too), but it's a bit big and clunky on a small PEN (I have an EM-5.-PM1).