Ask a Midwest pilot how they feel about ALPA and how well they protected their jobs when it came down to the wire. There are good things about a union, and ALPA has some of them like you mentioned above. The organization as a whole is not a real union - it is an association of disjointed work groups sometimes fighting against each other.
Ask a Pipefitter or a Steelworker about their union and the real power of a union becomes apparent.
I was an ALPA member for 14 years. When I was a member I went on strike for higher wages and watched all that we had gained go down the toilet when my company was forced into bankruptcy. I knew that our power was directly related to our solidarity. I watched ALPA do some good, but I mostly viewed it as a necessary evil that came about because the company would not treat us fairly.
If the company treats us fairly, I don't see a need for a union. The jetBlue pilots agreed and have one of the better contracts in the business. If we are treated unfairly when the company becomes consistently profitable, we will follow the path that many have before and organize. From those that I have spoken to, it will most likely be an in-house union.