So is JetBlue's Mint class worth it? If you're on a five- or six-plus-hour long flight, but especially if it's a red eye and you'd like to take advantage of the lie-flat seats to have a comfortable sleep session — then, yes, it's very much worth it. Or if you're just looking for an affordable first-class option, I'd recommend it.
But, in general, if you plan on working or just being awake the whole flight, I'd say go for coach — but splurge on one of the Even More Space seats for the extra leg room and early boarding. You can still enjoy the free WiFi, charging outlets, free snacks, and inflight TV for half the price (or less) of the Mint class.