yannisg : I went tubeless for the first time this July when I purchased my Surly Ogre. Initially I was not impressed at all. I suffered several flats within the fitst 4-6 weeks of use and had to replace my rear tire 2x. Right out of the gate the first flat I experienced was so bad the tire could not be plugged. There was goo spraying all over the place while I waited in vain for the sealant to do it's job (which never happened). I had to remove the tire, clean up the goop, remove the tubeless valve and install a tube to get home. The tire immediately went into the trash because it could not be repaired. What a PITA! My 2nd flat wasn't much better. Once again the sealant was spraying all over me and the bike, but a large plug was sufficient to fix the puncture. No tube required, but it was a mess. I was really upset and starting to wonder why people liked tubeless tires so much. The third puncture was small enough so that the sealant at least had a fighting chance of doing it's job. The sealant initially worked to seal the hole... temporarily. A few minutes after I thought the punture was sealed it started to leak. It went back and forth between sealing itself and then opening up again several times, so I finally pulled over and threw a plug into it. The plug sealed it, but I was pissed and seriously considered going back to tubes.
Before ripping the tires off and going back to tubes I waited until I had a cooler head to think things through. I concluded that 2 out of the 3 punctures likely would have happened even with tubed tires. Assuming that's true, how would my situation have been better or worse with tubes vs tubeless? In both cases I would have had to fully remove the tire, change the tube, put the tire back on and then pump it up. My first puncture required the same amount of work as a tubed tire (with some added mess from the sealant). However, the 2nd and 3rd punctures, while really inconvenient, required nothing more than a plug and some CO2 to reinflate. The punctures were repaired quickly and I was back on the road in much less time than if I had a tubed tire.
I ultimately changed to a totally different tire and haven't had any issues since. Yes, I've had two more punctures since swiching tires, but I didn't even know it until I got home. The selant did it's job and both punctures were easily repaired with plugs.
At the end of the day I've concluded that tubeless isn't the "be-all, end-all" solution I thought it was... but roadside punctures are definitely easier to repair than tubed tires. I've also learned that all tubeless tires are not created equal. Some tires puncture easier than others, some will seal easier than others. I'm glad I stuck with it and am now quite happy with my tubeless setup.