I have had the same old tread-depth gauge for 25 years. Purely mechanical, probably cost $2 back then and small enough to clip to your shirt pocket. But when I saw this on Amazon, I put it in my wish list and waited and waited before putting it in the cart. It was priced right but the shipping would push it above the "what the heck" level into the "will I really use it" category. In a moment of weakness one day, I decided to take the plunge. Click, click, click and pretty soon it was in my mail box.
I have tested it on my aging BMW and low and behold, I am in trouble! It is time to "re-tire..." Forget about the shipping charges, now I know I have tires that are right at the limit of safety. For my money, this gadget has already paid for itself!
It's easy to use. It's accurate and precise (i.e., the readings are reproducible) and it's seems made well enough to last a few years. I especially liked the spare battery that came with the kit.
I own a lot of cars so having a tool like this really helps.