They aren't bad. Not the best, but aren't bad. They tend to be on time, tend to oversell at busy times, and tend to not lose luggage. That said, at Newark they have some of the rudest, nastiest customer service people known to God and Man. In Cleveland and Orlando they are very nice. If I didn't have to deal with the nasties at Newark I would be much more likely to use them exclusively. But because of the nasties, I try to fly US Airways out of PHL as often as possible.
Anne