Fantastic repair kit
Like a dunderhead I ran over some roofing nails with my kubota tractor and the tires kept going flat every 2 days. Well, 3 plugs later and I didn't love any air over the course of a month and in the winter nonetheless. I am very impressed with this plug set and have already ordered more. Can't say what it'll do for a car, but the tractor weighs more then a ton itself so I have confidence that this would perform well on an automobile.

Works well, but not recommended for permanent repair
The kit works well, but as the instructions say, the tire should be inspected by a professional as soon as possible. While I have used tires for many thousands of miles after they were repaired only with the plugs, tire manufacturers and the NHSTA recommend that the tire be repaired from the inside rather than just the outside. The recommended inside repair puts a plug in the hole and a patch over the area surrounding the hole. This is supposed to keep air from entering the rubber, which could lead to a bulge. The inspection by a professional, if done with the tire off the rim, lets him look for damage that is not visible from the outside.

why use it?
what bother me in the Product Description "Designed for emergency tire repairs " "Enables you to get to a service center safely "to do what? buy a new tire! if this thing can fix the tire why do I need to go to the service?if not then I'd rather use the the spare tire till I get to the service center and fix it.

It works
What more can I say than it works? Follow the directions, plug the tire, inflate. No problems. Oh yeah - always go for T-handles on these things. Much easier.