I've got the 9mm version that takes Glock mags. It's sitting a few feet from me right now in that "awaiting repair" state.
I attempted to adjust the front sight and I broke that flimsy plastic front blade while at the range. I finally broke down and ordered up a replacement front sight from the guys at Blue Force Gear along with a tritium front sight post for the thing. Need to grab a few bits for my Dremel before I get to work on that project.
I got to run about 300-400 rounds through the thing before the front sight broke -- which is really my fault that it broke. It's certainly a hoot to shoot! I ran into some problems shooting 124 grain Speer Gold Dots out of it, but that was a lot of out-of-spec not-for-LEO use stuff. Never had an issue with any brass cased ammo. I'll do some more experiments with various HP ammo once I bring it back online.
Adding that buttstock extension really helps, too. Out of the box it feels like it was made to be ergonomically correct for a 10 year old boy. I'm not a big guy (5' 9") but it was a bit small for me. Workable, but too small. That little 1" extension is great, and it still has the same OAL when folded up.
I bought it as a plinker, but after getting to rock-n-roll with an MP5 I realized it was actually a pretty serious tool, especially when outfitted with 30 round Glock magazines. Now, I might be overly paranoid, but I don't like to travel without a long gun of some type, and this fits the bill pretty good. You can check into a hotel w/out anybody seeing anything that screams "HE'S GOT A GUN WITH HIM!" and I really like that. Fits into a laptop case nicely, BTW.
If I came across a good deal I might snag one in the .40S&W version. I really like it.
EDIT:
It was also really funny watching the local PD upon brining it in for "safety inspection." Apparently I was the first one to bring one through the Kent County's Sherrif's department. Rather than ask me how it worked they fiddled with it, in my view, until they figured it out. Waste of time, but quite amusing.