I am a serious frequent flyer who switched from Continental OP where I was a gold elite to jetBlue.
I could not be more satisfied.
The perks of elite status are not worth much if they are virtually never available.
1. Upgrades: These were a huge reason to attain elite status on CO. My experience, though, is that upgrade availability has diminished to the vanishing point. From Oct 2005 to Feb 2006 I went 0 for 26 on upgrades.
2. Mileage bonuses: As a gold elite, I received a 100% mileage bonus. The only problem was very limited award seat inventory, especially for a family of four, which is how we primarily attempted to use our reward travel. The fallback was "EasyPass" which negated the mileage bonus by doubling the amount of miles needed to book award travel. Even with EasyPass, it was virtually impossible to book an NYC-SFO itinerary, and EasyPass required 200,000 miles for four seats!
3. Elite Boarding: This still remains but is far less important to me than a decent amount of legroom in coach.
On jetBlue I was happy with the pre-conversion legroom and am basking in the post-conversion 36" seat pitch in the front of the plane. I love the seat which is far more comfortable than CO's coach seat. The PTV's are nice, too.
Regarding TrueBlue, as NYFL pointed out, earning points is comparable to the legacies (ecertainly if you take into account "EasyPass").
Finally, jetBlue has award inventory available. My family and I have booked 3 rt award itineraries from JFK to the West Coast in the past year. In each case we were able to book our preferred itinerary.
Finally, yes, there is no airport lounge a la President's Club, but to me the experience in the plane is much more important than on the ground and if you are flying coach I don't think there is a better choice for a frequent flyer than jetBlue.
Although B6 is thought of as a leisure travel carrier, it is actually perfect for the business traveler on a budget, in the sense that the walk-up fares are generally far less expensive than on the legacies.
One final comment: I love being free of the upgrade agita that grips every legacy elite passenger. With jetBlue I know I will have a good seat right from the moment I book it.
Comfort, peace of mind, a very reasonable price, and a perfectly fine domestic frequent flyer program. That's jetBlue in a nutshell.