[super__dan]

I have one and think it's great, as long as you're not expecting too much. I also think the benefits are physcoligical.

Firstly you need to make sure it's on a perfectly flat surface. I have a glass topped table which I Mr Sheen before use.

I use it for setting all the cambers every now and again (as they do move some). Now I always run -1 deg everywhere and whilst if that's not bang on I doub it makes much difference, in my mind I really like to know that it's the same on all 4 corners! It also put my mind at rest that the rear toe in was accurate and equal both sides.

Lastly it's dead handy for setting the front end of the car up to ensure you have correct toe in (0) and equal lock both ways.

Mine was £24 + P&P.