andrewclaus

It is. I tried it once and almost immediately hit something too large for the sealant to work and it sprayed goo all over the bike, me, and my clothing.

The flat protection you choose depends on where you ride, how hard it is for you to fix flats, and what weight penalty you're willing to incur.

I can fix a flat in less than ten minutes, I'm usually not in a hurry, and I generally ride in pretty decent weather, so I don't use any protection. Some days I'll get up to three flats, sometimes I go months without one. During my commuting days, I used and liked Tuffy liners. The problem I had with them was they could eventually wear a hole in a tube, but only after a thousand or more miles, when it's usually time to change the tire anyway.

Liners and heavier tires put mass at a bad place on the bike, where it may affect handling noticeably at higher speeds.