I've got the C model and it cycles and shoots everything I've run through it including round balls. Shot them accurately too.
I've owned two Glocks (17 & 22) but never could warm up to them, that and you aren't supposed to shoot cast bullets in them... The M&P does everything the Glock did better. It even looks better than a Glock and the grips are actually comfortable.
I'm not a big fan of plastic guns but I can not deny the usefulness, reliability, accuracy, durability, lightweight or capacity they are capable of. I like 1911's but I've only had one that was as reliable with every kind of ammo I've run through it.