Thanks for all your words of warning. I sort of feel compelled to answer.
It's a new mid-rise lift which means it lifts the car about a metre. It's for personal use and there are companies that sell quite happily to diy mechanics (and I have to say, provide excellent telephone support). The ramp comes ready to use with no assembly other than connecting the hydraulic hose. The mechanical side is very simple. Two big hydraulic pistons, with a hydraulic release valve, and an automatic shut valve in the case of rapid pressure loss (e.g. if a pipe blows). The lift locks into place mechanically using a simple steel tooth retaining system that needs compressed air to release it. You would need to be simultaneously activating the air line (an active safety feature), as well as having a failure in both the release valve (a passive safety feature) and the shut-off valve (another passive safety feature) for the lift to drop. Or, maybe, one of the scissors would have to catastrophically snap, but even then, at least two pieces of metal would need to break. I have a nice pair of 750mm axle stands that I used to use for farm machinery with a farm jack. If I'm under there for any length of time, I will use these to provide a final safety net. That's one hell of a lot of redundancy guys.
Nevertheless, I spent about an hour commissioning it, checking and re-checking every safety feature, hinge, load bearing piece of metal and platform. I lifted an old car first just to be sure before I put my pride and joy onto it. Now - that said, I do intend to get the ramp 'MOT'd' once a year by an installer, just as a second opinion, but not on commissioning - I really don't think its necessary.
I was brought up around machinery. I love working on cars and I spend a good portion of my life under them supported by axle stands or ramps. I just want a bit more room.
I think that the most dangerous thing about this ramp is the electricity that supplies it! But I've kind of given up on getting an answer to that!