yes, the M&P can be magnaported. (more obvious now, after the link to the 9mm)
magnaporting really does wonders for a gun, as I've seen them in higher caliber guns and was impressed with the after product.
however, I dont see any of the calibers in the M&P 9/357/40/45 being so hard to handle that it needs this. personal opinion, anyway.
it is kinda cool, i admit... but be careful. if you start magna-porting your guns, prepare to keep doing it. let's say you "port" a .40 - if you get another .40, the recoil is going to be more than you're accustomed to.
dont get me wrong... you may have reasons to consider this, and if so, your reason may void out any sense i'm trying to make here.