I use it. We have a Nitrogen machine at the dealership I work at. I thought it to be bull before I started using it. My Audi TT I had was the first car I tried it on and the first thing I noticed was the ride was slightly improved (Low profile tires). Then my TPMS warning stopped coming on due to ambient temp changes!!(happened monthly before) General pressures did not fluctuate as much. We charge $39.95 one time then free refills!
Now my wife's and my Z have it. Not going back!!
If you think it's to much money to have the service you shouldn't be in this hobby!
I think we are priced higher then those tire chains also!
Also: For those who call it a scam...why does Nascar and F1 use it?? I guess those engineers are inferior to your wisdom!