Can't speak directly to the Ultralite, but I've not lost any down from my 3, all of which are in that "lite" series (4, actually - I also got a Mitylite for my wife when she went car camping with me one spring; she now uses it for camping out on the sofa bed when both kids, their spouses, and our granddaughters come see us.)

There's been the occasional feather work its way out, but never more than one, maybe two, during a whole trip. I think that's pretty normal for any down bag; my buddy's Megalite did the same thing for him, and I've lost 2 or 3 feathers from a down jacket I've had for several years.