I pretty much only bought into the M system with the original EOS-M because of the 22mm F2 STM. It's a gem of a lens. And having a large sensor in a small body, APS-C, with a fast very sharp prime with good ISO performance and a really easy interface, yet still can go in your large pocket, without being a smaller sensor format camera, is why I got it. They were practically being thrown away at $150~180 for the M+22 for a long while. If I had to pick another lens right now, it would probably be the Rok 12mm F2 EF-M. I actually don't like using large lenses with the EOS-M with the EF adapter. It totally defeats the point of the small body and is very awkward for me since it really isn't meant to be held like a dSLR or anything, and those big lenses you can adapt really make it hard to hold thing snicely. I prefer small wide lenses with it.