EcuFishbowl, it really depends on what you are planning to shoot the M&P for. CQB (Close Quarter Battle) were a Red Dot and iron sights are just the ticket... or.... Targeting bullseye or small rodent terriorist hunting which means a 4X magnified scope for longer (up to 100 yards) shooting. The M&P is a clone of the AR platform so it was intended for CQB wth some long distant shooting and this being a 22LR, well, it kinda limits your long distant due to the caliber size. Learning to shoot the M&P like its big brother, AR15, in a tactical mannor can prove to be a lot of fun, so try this route first, you have the perfect weapon for it. Then since you can swap things off it, get a scope and try that out as well and see what your fancy is. Either way, you picked the right weapon for the job... Keepem in the 10 ring.. Note, Red Dot requires both eyes open using your brain to place that red dot on the target, it's a new learning procedure, but try it, it is really fast and fun.
Remember the AR15 and M&P 15/22 is the Chevy 350 of rifles, you have thousands of build for all the different kinds of shooting needs. Thus it is still being used by our Military for its diversity. It is almost modular in design and you can build and do as you please. Also there are thousands of vendors that are making Mil-spec aftermarket parts for this rifle that the sky is the limit.. So enjoy the building process, it's almost as fun as shooting the darn thing... Later..