My wife flew Aerlingus and really liked their service.
My trip to Manchester from PHX last May was on Aer Lingus. It was a few hundred $$ cheaper than the other airlines, and when I modified it to stay 3 days in Dublin on the return trip it actually got $50 cheaper.
Changing planes in Dublin was a lot better than going through Heathrow (they lose at least one bag every time) if your final UK destination is not London. Leaving we were TSA cleared in Dublin which made the plane change in Chicago a lot easier.