Just saw one tonight. It was pretty nice. One of my friends over at the indoor range had one he just bought a few weeks ago. If I wasn't in the market for an AK I might get one. I was impressed with it but I didn't get the make.
The performance is what you expect from 22LR, occasionally you'll have shells that failure to clear the receiver and get caught within the conversion.
You'll definitely have to clean the upper better as there is plenty of unburned powder, depending on the quality of the 22 your running through the AR. Other than that it makes for some great plinking!
I'd like to get one as well. I can get a ciener or oly conversion for the same $$ - any opinions betwixt the two? I hear the Aguila SSS .22 LR ammo works really well in them because the super-long 60 gr is basically made for a 1 in 9" twist. I think it would be a pretty sweet accessory for my NFA 7.5" AR.