Not my cup of tea, to be honest; and since I have access to some FA weaponry courtesy of a Class III dealer bud of mine, I don't really have much motivation to get one.
I simply think there is too much liability involved with these things, good luck trying to use one at a range and not drawing attention. Heck, even the last time we had a FA shoot here at a private range the local sheriff's office showed up. Luckily one of the shooters is the chief of police of a local municipality, and was in his duty vehicle so there was no drama; but the deputy told us someone called in claiming it "sounded like a war going on" where we were only shooting one magazine every five minutes or so. Since they only sent one deputy to respond indicated that the sheriff's department obviously knew it wasn't a big deal; but the mere fact that he even showed up demonstrates that any indication of rapid firing will get noticed.
The bottom line is that since there are easier/cheaper ways to bump-fire, I'll save the $289.95 for more important things like ammo!
Cheers! M2