I've trained with three people who had a total of 5 of them. Mostly they sorta worked. I think they have a trigger problem or something that makes them eratic on firing.
One of those guys had two of them and he never had any problems for a year. He left Alaska and his Training Groups were sold out of state before he left.
Another was owned by a gal I trained with, who then sold it to another member of my training group. The gal had trouble with it before she sold it and the new owner has changed solenoids and triggers and it doesn't work consistantly. Been a lemon from day one.
Another guy I train with occasionally, has two of them that are inconsistant.
My Strongarms have been much more consistant than the Training Groups.
I'd put my money into Zingers or maybe the new Gunners Up.
Also the Training Groups are pretty big, heavy and clumsy to set up, and should be staked. They say not to use them unstaked, but you can.