OK, i'll give my account of my tubeless experiance.
the 1st time it was due to the bike I bought used had tubeless wheels and non-tubeless tires w/stans in them for puncture protection. They were a good set-up until I had the front tire roll off the rim in a lay-down crash one day. a goopy mess that would not re-seal, so had to put a tube in..
2nd time, I set up a non-tubeless tire and a non-tubeless rim with a ghetto stans set-up. worked fine until I had a sidewall issue with the tire and it leaked stans fluid everywhere. I could not get the new tires to hold the bead, plus it was a pain to set-up the tires at 1st, and I really did not run the tires at any less of a pressure I did when I had tubes.
I weigh 255 and run my psi at 35 rear and 30 in front, any less and it feels wrong. I have no pinch flat issues and get plenty of grip at this psi with my tubes. I get my tubes for $2 each at price point, and usually if you have an issue with a Stan's set-up on the trail you need to use a tube to get you back to the car anyway. So for now I avoid the goopy mess, expense of stan's fluid, and the pain it getting them set-up... If I were a lighter weight and wanted to run my psi at 25 or so, I would look at tubeless again...
I may down the road try a true UST set-up with both UST rims and Tires since I am sure it is a much easier way to go.
that is just my experiance with it, others I know love tubeless both ust and/or stan's conversion set-up, but for me, it is really more of a pain with little (if any) gain.