I bought 5 of the Glock 17 magazines to try out. I have plenty of OEM mags, but these ones will be the range beaters. If Magpul ever releases a .40 version I will buy some of those as well for the same purpose to keep from beating my duty magazines up.
Some observations:
The body feels stiffer than the OE Glock.
There is no large 9mm markings on the magazine. The follower and the body both have very small print. This will be a negative if/when the .40 versions are released. The OE Glock mags are way better in that regard.
I don't miss the witness holes, but I don't shoot competitions that require me to load x number of rounds. Knowing the magazine is full is good enough for me.
The floorplate is really nice and much simpler than the OE design.
If there was one area where I think the GL17 magazine will do better than the OE design is the feed lips. If Magpul got it right(which I'm sure they did) the feed lips will hold up better to heavy use. The metal and plastic combo on the OE mags likes to separate after heavy use, eventually exposing the steel liner. Once the liner is exposed, the OE magazine's feed lips are a lot more susceptible to damage during a hard drop. Of course it's rare, but I've seen it happen.
I will pretty much use these magazines exclusively for my G17 so hopefully they work out well. If not I have OE mags to use as well and Magpul will take care of any issues.
For shits and giggles, once we get some triple digit weather here I'll leave a magazine out on the rear patio loaded and see how it handles the heat.