ive got a couple 22 pistols and the only advice i can give you is beware of any gun that has a 100% plastic mag!
ive had nothing but trouble with plastic mags and they die so fast its not even funny.
now when i am looking at 22 guns that is the first thing i check for is if they have a metal mag.
or at the very least metal feel lips on the top.
chiappa is the one i know for sure has a plastic mag.
as for your original question, M&P 22 is nice, i have one, love it. The GSG/SIG 1911-22 is real nice, i have one of those and it runs like a dream.
sig misquote's from what i hear have or have had a problem with the slides breaking in half (??)
the ICCS glock knock off is nice but realllllllly small in the hands, and the reviews on it rate it as nasty bad for reliability.
the local gun store up here has had one in stock for like 3 years if that is any indication on how good they are....