It's just the same thing over and over-- people have never run tubeless, but they heard third-hand from one guy that it's a "hassle" so they discount it. The drawbacks are expensive tires, and a limited selection. That's it. Everything else lands in the plus column, in my experience.

And I really, really want it to catch on, gain in popularity, so the costs will come down. MTB tubeless tires cost half as much for 3x as much physical tire. I can't keep spending $90 on a pair of tires every 3 months. It's killin' me.