We have a Doyle UPS
It's hard to explain the quirks, but overall, if adjusted properly, the UPS sail is great to look at and makes for a nice sail on a reach. We received our sail with too small of a furling drum (Doyle did replace it- but we still wonder if it's too small). Only with some luck are you able to completely furl so that you can tack easily. Typically, we run out of fuling line before the sail is completely furled. We use 1/8" line and can't go smaller. Still, we do like the furling feature over a genaker w/ a sock that you have to manually handle.