I haven't tried using sealant. But I hear it's a mess when it doesn't work and you need to fix the tire anyway. What tires are you using? I use Continental Travel (or City) Contact. They work great for me. I used to have lots and lots of flats - like every few weeks. But that was on my old road bike with skinny tires. I fixed that problem by using Mr. Tuffy liners. Then I got my present bike, no liners but the above tires. I had two flats the last year. My routes are frequently through constructions areas and other places in the city where there's lots of stuff in the road. About 10K+ miles/year.