JetBlue is a great option if you don't have anyy other options.
If I want to connect to JFK from ROC, I HAVE to fly JetBlue. No one else makes the run at all.
AA only flies to ORD. UA only flies to ORD or IAD. DL to CVG or Atlanta. I can get to LGA or EWR, but not JFK.
Complain all you want about JetBlue, but it came in a filled a niche that was ignored and managed to force the other airlines into EWR or LGA lower their fares.