ThomasH to date neither my Colt M4 .22 or GSG-5 has had one problem concerning the actual "safety" of the gun firing out of battery or anything like that. Why people like to attack another firearm when theirs is attacked is beyond me. IMO, a rimfire should never "blow up"; I'm amazed that S&W hasn't issued a nation wide recall over these things. The potential for injury is enourmous with these guns.
I own a GSG-5. IMO. It's a poorly designed, overpriced, pot metal, POS. It's an airsoft rifle designed to shoot rimfire ammunition. Sure, it's fun to shoot when it works, but that's true of any firearm. But, it's even more picky about ammo then the 15-22. Maintenance and cleaning is a royal PITA. If you tear it down for a detailed cleaning more than a few times, your likely to have to start replacing screws as the cheap pot metal and aluminum parts and cheap fasteners start to strip out. I've had a few OOB's that required full detailed strip to correct. Granted, the OOB's didn't result in any damage to the rifle, but it still happened. About the only thing well designed are the sturdy magazines. The ONLY reason they were so successful is they were pretty much the only ones in the game. Even if my GSG-5 ran reliably, it wouldn't change my opinion on the design. I still have fun with it, and the kids like it, but it doesn't change the fact it's a POS.
As far as the Umarex/Colt AR's, they are of similar design and materials. In fact, the design is even worse than the GSG-5 in some ways.
Contrast that with the S&W M&P15-22. Simple design. Every thing it needs, nothing it doesn't need. Uses standard, widely available fire control parts. Can be field stripped exactly the same way it's big brother does. Has all the same controls as it's big brother. The only real downside to the 15-22 design is that it doesn't match the weight of it's big brother. But for some, that's a benefit.
I'm sorry if you feel hurt that I think the GSG-5 and Umarex/Colt are substandard crap. It's nothing personal. If you're happy with them, enjoy them. Just calling it as I see it.
BTW, the first few runs of GSG-5's had tons of problems. There were alot of people that had to send them back multiple times for warranty service.