I personally was not a fan of the 5Dm2 either. I have never owned one, but I have borrowed one several times to test on, I've always been annoyed somehow with how the device handled. In the same way, I'm also not that fond of the 50D. The 5Dm3 however is different, from the first moment you pick it up, it just feels a lot more right. And it's capabilities are stellar!
The official ICS release for SGS2 supports DSLR Controller without root. It should be available on KIES.
Only Honeycomb and Ice Cream Sandwich have a gallery that does this. If DSLR Controller is being used on a Gingerbread device, the gallery app will not offer to be opened. Also beware that the galley app (as far as I know) only imports the JPGs.