819 with UST has been faultless over 7 years IME.
819 with non-UST tyres has been easy enough but had to cut the tyres off as the latex had dried out and sealed them totally after 2 years.
Now have 2 wheels with Stans. Flow with UST tyre – went up easily, stays up, no problems. Arch with Racing Ralph 29er non-UST & rim strip – err, went up easily, light as you like, no problem.
But … a mate has a set of Hope Hoops with Stans 355 & UST Schwalbe Furious Freds. One just won't inflate – gets to 25 psi and air escapes. Just can't get it working.
IME tubeless is great if you don't want to change tyres frequently, like others have said. Until the recent Furious Fred debacle I'd have blamed user error, but as I have failed to get it to work that can't be right 😉