As much as I've heard good about them, I've heard equal amounts of bad.
(As in people not finishing races bad).
I spend enough energy trying to stay on the bike without worrying about remembering to air up my tires every time I go ride or cleaning slime off my rims whenever I change a tire.
I'm not opposed to trying something new, and they sound very appealing (when they work right), but I bought a new bike so I wouldn't have to fuss with stuff.
Knock on wood, but I've had very good luck with Ultra Heavy Duty tubes and slime so far, so it's hard for me to justify spending $200 on a Tubliss system when I can run what I have for around $50
Plus I've got to use my fun money to buy some new unbreakable levers after last race.... oops...
I just swapped my first tire on this bike, I'm going to try a AT 81 rear.