As said, its still a grey area as they are relatively new on the market (well, they have been about since the mid 80's, but only on the porsche 956(?)) but we have been plugging them for a couple of years and not had a problem, Bridgestone rep approved anyway!
We have even had a few major repaired, they are no different to a normal tyre, its just the sidewall is about 8 times thicker than usual.