Didn't even think of PWM. I personally think that JetBlue could do well there, it is far enough away from BOS and MHT to be competing with them, and if B6 can make BTV work with all 500000 people in the state of Vermont, then PWM should work. There is minimal competition on mainline equipment, like BTV (DL has 4 daily MD-88s, NW 2 daily DC-9s, US Airways 5 733s daily, which equates to 10 mainline flights daily (BTV has 8, 6 on U, 2 on UA; doesn't count B6). All-in-all, PWM has slightly more capacity now than BTV, but there is a much larger region. I could see 2 JFK flights working immediately, and maybe adding a FLL flight when that operation grows.
As for MHT v. PVD, each have their own pros and cons. I would always go MHT over PVD, as MHT is a 40 minute drive for me while PVD is 100 minutes. But, if you lived on the South Shore, the polar opposite is true. Each airport has their advantages and disadvantages. MHT is much better suited for ski charters, while PVD already has had Air Luxor A330s during the summer. While I don't think MHT will become the next SFB to the extent SFB is currently (whenever I am at Disney, it seems like 10% of the families there are British), I could see a few years down the line maybe a charter 757 for skiing during the winter. MHT will not become SFB though, with 767s, A330s, and 747s not being frequent visitors to MHT in the future.
Yes, JetBlue will be in the Boston market by 2005, it is all contingent on several factors. The first is how the industry plays out in the next 3 years. In three years, US, UA, AA (amongst others) might not even be around, or will/might be severly down-sized. This may be the opportunity to B6 to enter BOS. If not, they should be there in 2005 when the new Delta terminal opens up, freeing (tentatively) the pier on Terminal C they currently occupy (I still think they may keep some gates there though..., since 22 might not be enough from DL, SkyTeam, and Northwest/Continental, contingent on the codeshare goes through.)