We've been flying USAir for years out of Allentown and Philly. Though we have had our share of flight delays, etc. with them, I would say they have been just fine. I could recall positive as well as negative incidents with them, with the latter not being much more than annoying. We flew a few weeks after 9/11, and with flight cancellations and rescheduling, I was rather peeved with some things, but in the end, the flights were fine and I was able to sit with my 2 &4 y.o. children! OTOH, we had been abandoned in FL by a charter outfit, and the US Air rep was able to get us home on a Sunday flight, during spring break, direct to Philly, for what I thought was a reasonable cost for last minute/on the spot reservations.
So, I'd encourage you to try them out!
Sharon