I did a quick review on them on here somewhere. Several of us have had good luck with them for 'fun mags', but another guy I know was really disappointed (wouldn't work with his funky mag loader, he couldn't seem to get more than 15 rounds in any of them, etc).
Grab a few and try them out, see if you can live with the 'hard to load' thing and if so... you're getting 3 for 1 compared to OEM glock mag prices.