I am planning to purchase a M&P 15-22 soon to go along with my M&P 15 Sport .223/5.56. I absolutely love my sport. Deff. should check those out if you don't feel the need to have a dust cover and forward assist... I didn't.
Could just buy the upper to make mine a .22... but I like the thought of having two separate dedicated firearms... but thats besides the point.
Just my .02$