For several years now I have been riding tubeless on my mountain bike and the benefits are more than obvious. You very rarely get a flat and when you do, a bit of superglue is all you need to get home safely. If all else fails you can always use a tube. There is a minor price to pay in that it is harder to remove a tubeless tire (or install one) but proper technique goes a long way here as I found out recently.
The myth about not being able to pump the tire or not being able to form a proper seal is also just that. I have never had any problem and believe me, my upper body strength is not there. I also never used soap or sealing liquids or any other messy substance. Just mount the tire and pump it up. Easy as hell.
I get flats a lot less often on my mountain bike than my companions do. As a matter of fact it took almost two years before I first had a flat and by then the tire needed replacing anyways. So far I have had only three flats in all the time I rode my mountain bike.
The first time, it took me a long while to remove the tire and insert a tube but most of that was due to inexperience. I also messed up the valve and lost some O-rings but that too is a thing of the past. I have made enormous strides in properly installing and removing tubeless tires. The key is to use the palm of your hand and not your fingers!
Now after all these years I switched my road bike to tubeless as well. It works like a charm. I used Hutchinson Atom tires and they ride as well as any other tire I have ridden. I read somewhere that tubeless was nice but not ready for prime time yet. I wonder who wrote that and why, because I certainly can't tell the difference. The Atoms ride as well as my Michelin Pro Race 3's or any tubular I ever tried.
I think the hoopla surrounding tubulars is largely just that. Tradition! Sure you feel a difference. Who wouldn't when you suddenly ride a tire pumped to 145+ psi? The pressure difference is very noticeable on your bottom parts.
But why use an air chamber, which is supposed to give you cushioning and comfort if you are going to pump it up until it feels like a steel wheel anyways? Maybe for a short Cat whatever race, such things may work, or if you are a pro and have a butt of steel, but why sweat it? A tire is supposed to give a bit. That is why we use tires.
Just remember that many pros suffer saddle sores and other bottom bruising ailments and these sometimes force them to stop racing (at least for a while). The enhanced shaking also takes its toll. You are more fatigued when riding such high pressure contraptions. And the gain? Less rolling resistance? According to carefully controlled tests that is illusionary too. Clinchers have less rolling resistance than tubulars. It appears that whatever you gain from less tire flex you lose from stretching glue.
Tubeless is the best of both worlds. You can ride normal pressures and you won't get pinch flats. If you do, you can fix it as easily as fixing a flat with a clincher. I have not read any reports about using superglue but I do plan to test it should I get a flat. If that works, things are even easier. In any case, when you get a tear in a tire, any tire, you will need to replace it anyways. And a good tubeless is as inexpensive as regular clincher.
Yesterday I rode a 2X20 on my rollers. I averaged well over 350W during the efforts, and things went very well. Last night my right knee was a bit sore, but nothing too bad. Today I went on a 8.8 mile run. My timing was perfect and I managed to find the optimal weather slot in between two nasty rain bouts.