I used them for a tire repair after one of the big-name places refused to fix a puncture because it was supposedly too close to the side of the tire. It was practically a brand new tire and I didn't want to have to buy a new one already. So, I plugged it myself and drove on it for a year (so I'm pretty sure the tire's not going to blow out). The recommendation not to repair comes from the US rubber manufacturer's specifications (i.e., run by the people who make and sell tires), not from a safety agency, and that's why the big guys didn't want to fix it - they'd rather sell tires than fix old ones! Making the specifications extra-stringent only benefits them. I learned that in England tire repair specifications are written by a safety agency, not the people who sell tires, and my repair would have been considered safe to do there.
Anyway, the plug wasn't a perfect fix - it really needed a patch - and after getting frustrated with dealing with a slow leak and having to pump up that tire every few days, I came to Llantera El Rancho. They fixed it for me quickly, inexpensively, and with a smile. I will probably buy new tires when I next need to replace mine, but this will definitely be my go-to place for tire repairs.