I bought a Do-All Arial Assault 3 because of the velocity potential, and so far I really like it. It will really fling them out there with the spring cranked down. Got the wireless remote too, so I can shoot from all angles. After about 200 to 250 rounds it started braking a few targets and I had to do a little adjustment - wasn't hard - and no problems since. An acquaintance has I think a White Wing and he has to tweak his every so often as well. They are not as robust as the commercial machines, but they don't cost like it and you don't need a truck to move them either. I have mine and the battery in a yard wagon and I just tow it back to the pipeline with the lawn tractor and let fly. I did not have to add stabilizers to the wagon. I took it over to my buddy's for a shoot and just picked it up and set it in the back of the Jeep, no problem.
I got a Battery Tender auto battery maintainer to keep the battery up to snuff. I love those things.