I received the on-wall M22's today and got them installed, except for hiding the wires in the wall. To do that, I need an RF remote first so I can move all of the electronics and wires to the other side of the wall into a closet.
Cons: Less bass. Noticeable especially in music.
Pros: Better sound stage, possible because they are spaced a little further than I had them before and higher nearer the screen. I like the sound. One of the things I wanted with the bookshelf M22's was better highs. These have what I was looking for. Also they sound better than the bookshelf M22's paired with the VP100, nearly a seamless transition.
Can't wait to get a sub and see what kind of difference that makes.
Edit: almost forgot the picture.
Edit: Oh and one more thing, there is 47 inches between the speakers. I can move up from a 37 to a 47 inch tv which is about 46 inches wide.
I sure wish the wall color would reproduce correctly. It actually looks like a dark orange.