Waste of money.
I had one for all of a week and tired of it. Luckily Tesla had a fairly lenient return policy and took it back for a full refund.
First off... the thing is near useless if you can't launch without wheel spin. ANY WHEELSPIN AT ALL will mess up the test results. They say this much in their instructions.
Secondly, unless you are a) making changes to the car that are increasing or decreasing power, etc., on a regular basis, and b) have a nice empty strip of road that you can do whatever you want on, you really won't be able to get much use out of it.
Sure it's fun to play with but it really is just that, a toy that you will bore with.
And really it's not the easiest to calibrate properly either so even if you do launch w/o wheelspin chances are you aren't going to get accurate results.
Just go to a dyno or track instead.