I'd like to shoot one. But I doubt I'd buy one... since it would have to be a pre-1986 model. And if you get an older select fire weapon, you better make sure that it's not "shot out", and if so, you better make sure you can source parts for it. This thing is too rare for that, IMO. If I ever buy a select fire or full auto weapon, it will definitely be an H&K MP-5.
On a gun forum I used to go to, a guy claimed to have fired one and said he'd even met Gerry Baber. I don't think it's junk at all. Apparently it's primarily made of stainless, with some titanium components. The design and engineering are said to be top notch. I don't know much about them, but from what I've read, the AA-12 is a well made (and unusual) weapon.
Not that I need an MP-5 either. But I've heard that a pre-86 AA-12 goes for over $12 grand. And I can't imagine paying that much for something that I MIGHT fire a couple of times a year.