I did that for a while, and thought it a great success, until the problems added up and I soured on the idea. The problems I found were:
--patches won't hold to those tubes. I know, some people say it is possible; and obviously if the tubes really do self-seal then patches arent necessary... but....
--the sealant doesn't work on high pressure tires; the threshold seems to be around 70 psi. Again, some people claim otherwise, but my experience is what it is.
--the sealant doesn't dry in the tube, but it will eventually dry in the valve stem, making it impossible to inflate.
I think I have them in my wife's 3-speed, which is a good use for them since she is willing to inflate the tires herself but is not willing to do more elaborate repairs. Otherwise, I've given up on them.
I use automotive sealant and have not had an issue with the valves getting fouled, key seems to be with following the directions and riding after application to distribute the sealant.
Good point that it does not work on high psi tyres or when you experience significant damage and I always carry a spare tube regardless.