Heya,
I have the EOS-M with 22mm F2 lens. I picked up a few extra batteries and the Fotodiox EF/EF-S adapter (cheaper and works fine). Very handy little camera. It has great image quality. It's easy to use. I got my whole setup for $285, because I found a used one on ebay with some scratches.
What I learned while using the EOS-M so far, is that it has two big things that you have to be aware of before you sink money into it. 1) it's small, so holding it and using it with other lenses is very different since there's zero viewfinder and you use the LCD for everything, this is not a perfect feel for me, I had to really get used to it. 2) It has very slow autofocus, I mean super slow. It's not good for action. It's great for stills, landscape, portrait, etc. But don't try to take a picture of a herd of passing bison or something. If you can get over those two big things, it's an excellent little camera.
I went with the EOS-M because it can share my EF lenses.
I mainly use it for it's 22mm F2 lens. That thing lives on there. It's a handy little compact camera to pack when I'm not wanting to lug my bigger cameras. I use it along side my 5D classic (gripped with RRS L bracket, huge, heavy) and 650D (attached to long telephotos). It's handy to have a small camera that literally fits in my cargo pants pocket or dangles around my neck without bulky weight.
It's probably not the best value at $250. But if you want a compact mirrorless with great lenses that can use your EF/EF-S lenses, it's the only option at this price.
Very best,