Hah, I actually fell off the Poma at Copper earlier this season, and it is not the first of these lifts I have ridden. Almost missed the grab, managed to hold on but couldn't get it between my legs in time, held on for a minute or two before giving up and hanging my head in shame. The next time I rode it, it lifted me a foot or so off the ground but luckily I held on. It's one of the few that makes me nervous on a good day, don't want to be jeered if I fall off when there's a big line!
I had a nasty experience on the Breck tbar once but not because it is difficult in and of itself, mostly because I was riding it with a 6'+ tall dude and the kid in front of us wiped out. I almost managed to jump over the fallen guy with the help of my large tbar buddy, but in the end couldn't clear the deadfall.