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Oops, I seem to have lost on the "book cheap holiday travel tickets" plot. Any advice on the relative merits of Song (Delta) vs. JetBlue vs. Southwest? Any other options worth considering for BOSish to SFOish? (It seems like I can get around $400 cooked on any of the preceding options now for the dates I want to travel; AA is $550+, which isn't worth it just to get useful FF miles, and I can't reasonably travel on miles.)