I've used it in bicycle tires, and have had really good luck with it. I used to get flat tires on a trail on a regular basis...between the Slime and a plastic shield that goes between the tire and the rubber, I never had a flat again (to this day, actually).

When I was new to driving, I asked a tire shop guy about using it in car tires, and got laughed at...he then told me to never use it 'cause it gunks stuff up...

*shrug*