"Also, it can be tricky to find mags and holsters for it."
Only if you are looking in Tibet. All the major holster makers make holsters for the M&P. I have it on good authority S&W has no shortage of mags for sale.
Otherwise, a great buy - alot easier for most smaller hand (i.e. female) shooters to get good consistent groupings with."
Also great for guys with big mitts. The changeable grips work for just about any size of hand. The M&P has a much better grip than any of the Glock iterations I have held. Sights are made of metal not plastic as are the mags both of which are improvements over the Glock..
If you can find a Glock that fits your hand than go Glock. If you can't, the S&W M&P is a very good pistol to look at.
Take Care
Bob