I recently took JetBlue from JFK to LAX for business and it was a most pleasant experience. The check in process was normal, apart from the fact that they had kiosks that were produced in the last millennium, so they worked a little faster. Onboarding process was routine - usual for America (IE everyone has carry on luggage, takes forever to stow). Once settled, there was ample room under the seat for my personal item, the Wifi is fantastic (and free) for an aeroplane and they even had healthy meals for purchase that were edible - a first for a US carrier as far as I have experienced. The planes are new and very comfortable, I was a few rows from the back and it was not bothersome at all. The service was not overly friendly but was normal - efficient and sufficient.
Flight was on time, and I am yet to have a negative experience on Jetblue - having flown them approx. 15 times.