In reply to supersteve:
Been using for some 8 yrs, originally in a mt bike, now on a hybrid. They work.
However, ime, firstly, they are heavier (tyre/self heal tube combo - tube rubber is thicker and weight of sealant) than both normal tubes in tyres or tubeless tyres set up and the sealant is thicker than tubeless sealant. Maybe psychological but the rolling resistance seems more when using self heal tubes.
Also, when they puncture they can, depending on what caused the puncture, lead to quite a lot of sealant ending up within the tyre before it seals to give a sticky gunge and cause problems and extra time in removing tube and cleaning up if patch repair needed later or when changing tyres, etc. Sometimes even the sealant sticks to the rim where the tyre beds onto the rim and this has to be cleaned to get tyres to seat properly after changing.
Valves can get gummed up, though rare, and inflating or just checking pressure seems to always lead to some sealant coming out of the valve and more so than I ever get coming out of a tubeless setup.
I only now use on a hybrid for convenience - I like to change tyres often on that bike depending on season/circumstances. When not punctured with the self heal tubes, changing tyres is so much quicker, easier and less mess not to mention waste of sealant c/w tubeless.
The plus of course is thorn like punctures repair themselves before you actually were aware you had a puncture so no stoppage on an outing. Tubeless though are the same for simple punctures so it really depends on whether the downsides suit or not. I have had at least 3 punctures in a self heal tube without knowing until I remove tyre so they do work in my experience.
Are they better than tubes - no active intervention generally as self repairs for simple puncture. Are they better than tubeless - not if set up right and you know how to repair larger cuts with threads.
Personally, I prefer tubeless on my bikes including mtb (don’t have a road though so can’t comment on that). Just my view.