I've shot one(an Arm pistol that is). It was back in '87. It was VERY unpleasant. Way too much muzzle blast. The trigger completely sucked too. It was spongy and creepy. The sights were pretty crude too. It looked like the design was borrowed pretty heavily from the AR-18.
Now before anyone goes jumping all over me saying that "it's a survival gun, whaddaya expect?" let me say this:
There is no reason to not make something well.
If I ever find a decent deal on one in good condition I'd get it just because it's odd, but there is a long list of other things I want more. Franky, they're not much more than a novelty. Make it go bang a few times, marvel and the weirdness, clean it and put it away.
edited to be clear on which monstrosity I've actually shot.