USGI Ar mags?

Very impressive. I've seen the ads on the ar15 site regarding the magpul pmags and they themselves have a disclaimer stating that this mag is designed primarily for recreational shooting and not meant for professional daily use... bla bla bla or something similar to that.
"- Engineered from the ground up to be made of injection molded polymer.
- Patent Pending design allows for a more aggressive constant curve of ammo stack than found on other Nylon magazines.
- Made of "new to the market" reinforced polymer which is very strong and durable.
- Can be seated on closed bolt with full 30 rounds loaded.
- Snap cover protects feed lips during long term storage.
- Optional maglevel window version that can be read from both sides.
- Floorplate lock.
- Proprietary anti tilt follower.
- Debris grooves built into mag body.
- Molded in Black, Flat Dark Earth and OD
-Estimated retail price will be $11.95 for non window and $14.95 for dual Maglevel version.

NOTE:This magazine is not meant to replace metal mags for individuals who shoot daily for a living. They were made as a volume supplement to issue mags that can be made quickly, in large numbers with minimum variances in manufacture."

Obviously they might be understating their magazine's capability to withstand punishment. As strong as the magazines are, I wonder how well they'll stand up to the wear and tear on the magazine lips. As we insert and extract several thousand times, will the polymer wear faster than steel causing it to misfeed and jam?

I suppose only time will tell, but for ~$15, one or 2 might well be worth a try!

Thanks for the knowledge.

Cheers,

For the record, I have nothing against polymers... exhibit A: XD-9.

From MagPul themselves on ar15.com

"Let me start by saying this IS a legitimate topic.

Polymer feedlips have some issues to deal with when they are non reinforced with metal.

1. Creep when loaded
2. Cracking when dropped or during feeding
3. Throating of the feed lips by rounds being stripped.

So far the PMag has passed our minimums for all these.

Even storing the mag loaded for 60 days without the cover has little or no effect on the feedlips creeping. We have some PMags with over 2000 rounds logged on them with no signs of wear. Dropping a fully loaded mag onto the concrete feedlips down can sometimes cause a crack in the body but in all these cases the feedlips were fine and the mag ran without a problem,

Remember the PMag is meant as a semi disposable item like the USGI."

They are still prone to cracking, throating etc like any aluminum mags, but when viewed as a semi-disposable piece of equipment for ~$15, not a bad choice at all.
When the stores have the ones with the windows on em, I'll probably pick up a few. Here's the link on youtube with the same torture test for the windowed mags:
http://www.youtube.com/watch?v=4BA-EdEAHVA