S&W says the M&P9 sight will work, but the M&P22's sight is adjustable up and down, but the 9mm's sight is not.

Mine had occasional failures to load. That is the round fired was slightly below the energy needed to extract and load the next round. It would extract OK, but the slide (apparently) didn't go back far enough to load the next round. As the gun gets broken in, this is getting less and less. Of course, if I wanted to use premium ammo like CCI Blazer or Mini Mags it would work fine. I use that ammo in my 1911 Kimber rimfire conversion and it runs 100%.

Enjoy your new M&P22, they are a ball to shoot. I too have a M&P9, M&P22, and a M&P CO2 gun I got from Midway.