I had a pretty good first experience with Frontier.
I usually fly USair but someone else booked my flight.
I almost always have to gate check my bag because I'm usually the last one on, but since I volunteered my bag they let me board first. (That's a first for me!)
The seats were nice and the service seemed fast (granted it was a smaller plane.ha.)
I think I would still choose US just because of what I've heard about the flight time changes. That would mess me up, but no problems this time!