We flew with US Airways to Las Vegas via Phillidelphia in Dec. To be honest with you we would never fly with them again!! All of the flights were delayed by ay least an hour. We missed our connecting flight to LV on the way out, and we had no help whatsoever in trying to sort out another connecting flight. In fact their staff were downright rude. The flight attendants on the international flights were really rather surly, and acted like they would rather be anywhere else than on that plane. However the attendants on the domestic flights were pleasant and friendly.
While we were in the States there were lots of news reports about how US Airways had lost 1000's of pieces of luggage over the Christmas period!
Hopefully you will have a better experience with them!