Song has been one of my favorite airlines to fly with. I fly out of Boston. But with the merging back into Delta this spring, who knows how it will impact Song. Some things will change, others will not. My only problem with Delta/Song is that if you book early, you have to constantly watch to see how your flights get changed. You wil notice I say 'how' not 'if'. I have yet to fly Delta/Song and have no changes whatsoever. Sometimes they are miniscule, but still require a call to their CS line. Other changes can be big....taking a 2:15 flight, and canceling it, and putting those people on a plane at 6 or so. Yes, I understand they are supposed to work with you in that event, and they have been pretty good about it when it has happened to me. But, I am flying in Oct and have still not booked my flight. I'm waiting to see what other choices I have...JetBlue and SW.
So...if you can get a decent fare with Delta/Song...go for it. Just be sure to keep an eye on your reservations. Other than that 'little' issue, I have loved flying Song.