Not looking to threadjack Bob's thread but yes I have one and have been using it a lot before I get a real lift in. I'd agree with what 08mojo said. The only thing I will say if you are considering buying one, they offer the quickjacks in different lengths so buy the length most appropriate for your car. I got the smallest one on sale but its an inch too short to fit the jack pads of the M5. It'll work fine on the Mustang (jack rails) and Marauders (full frame). Since the Marauder is such a big car if I don't center them the right way it can get a little wobbly, I don't think I'd pull an engine or drop a trans using these. But all the work I've been doing so far, it's a serious time saver. Push button, car is up in 30 seconds, locked, done.
Completely agree, especially with the bolded text. You still have to be smart about lifting the car. If you plan to do extensive work, make sure you place jackstands for added protection if you are pulling an engine/trans.