I used Stan's sealant in tubes for a season and was pleased, but found that Flat Attack pre-filled tubes were a better alternative. Their sealant is gauranteed for 5 years so it doesn't need to be "refreshed" from time to time to remain liquid. The sealant is also supposed to be biodegradable which makes me feel all warm and fuzzy for using it. Despite many punctures, I haven't had a flat on the road in over three years. When a puncture occurs, the tire loses a little pressure, I stop and remove anything I find on the tire, add air or CO2, give the wheel a spin and ride on.
Marc