I have used it on clean rims and over old glue and it works equally well on both. For a road race or track bike I would recommend it. I am not sure your average triathlete could get the tire off in time during a race,
One pretty cool thing about it is if you can pull it off the rim it takes old glue with it leaving your rim pretty clean. I keep it in the travel bag so if I puncture during warm up I can tape a new tire on and have confidence to ride it. Again, the only con it that it is a real bitch to get off. No way my wife would ever be strong enouth to get the tire off the rim with it on. G