For me, they are very frustrating. Some issue or inconvenience always shows up. A missed connection, delayed flight, missing baggage, free-for-all boarding, very rude gate agents.
Unfortunately, I will be flying with them again in three weeks (two flights each way with connections) because the schedule works for me. I have heard that service has improved quite a bit, but my last four flights with them in May were a case study in delays and rudeness. Actually, I think rude is too nice - the gate staff were openly hostile to other mild-mannered passengers. I was embarrassed for everyone.
I hope it's better this time. Honestly, I think they are the worst domestic legacy airline.