Actually, they've done really well. We started off with short trips, just a few minutes, to get past the whole "V.E.T." thing, and we've been gradually increasing the time every week. Our tortie, Squeak, gets carsick after about an hour, so we're going to try some holistic remedies first, then we've got some anti-nausea pills from the vet as a fallback. I think they're gonna be fine.
(And truth be told avoiding the cat sitter is only a small part of the reason: I adore these two and suffer some serious separation anxiety any time we travel

)