As for restrictions, this flash sale comes with the typical fine print. Specifically, you'll have to travel sometime between January 16 and April 25. The discounted prices are also only for JetBlue's "Blue" fare, which doesn't include a checked bag, but does include the airline's standard in-flight amenities such as free Wi-Fi and unlimited snacks. There are no blackout dates, so that may make adjusting your schedule for a last-minute trip a little easier.
Having to book your flights (and figuring out other arrangements such as a hotel room) before the sale's over isn't exactly ideal, but there are indeed some good deals to be had if you're able to throw your regularly scheduled routine out the window and book a trip on the fly. If not, you can always keep an eye out for the next big airfare sale.