My favorite aspect to polymer magazines is the ease with which the feed lips can be given a cursory inspection for function. On the older metal magazines bent feed lips were the number one mag-related failure IME. Unfortunately this couldn't be diagnosed until you were actually shooting the gun. With a PMAG it's binary: the feed lips are either solidly intact, or they're cracked. That eliminates having to function check for a very common magazine failure.
I bought my own PMAGs and carried them through 2 tours in Afghanistan, rain, snow, ice, heat, cold, dirt, etc. They work, are durable, and they last. Under normal circumstances, they're also inexpensive. I only broke one, and I don't blame the mag. I overloaded a 30-rounder prior to running "ready-up" drills. During a lull in the drill I went to swap magazines with the bolt forward. Magazine wouldn't seat when I slapped it into place. I hit it progressively harder a couple times, to the point that my hand bruised (again, this was mid-drill). When it still wouldn't seat, I yanked it out and tossed it for another one. When I picked it up at the end of the drill the feed lips cracked on the back side of the magazine. Overloading had something to do with it; beyond that it was probably me beating the tar out of it.