I would agree with not choosing Arizona. Although it has some libertarian leanings (super gun laws AND moving in the right direction on pot, for example) it does have a large population. It also has some border issues that would complicate any secession movement.
But I think Idaho has NH beat.
I see some good things about ID. I think it lost for a lot of reasons. It is to a large extent, owned by the federal government. It has a very large religious fanatic population. More than any other state, it has a reputation of white supremacist movers (something some FSPers wanted to stay far away from), the state is dry, it doesn't have any major cities and it only arguably near 1 major city. The lack of jobs. For example, with NH and DE, their are tons of jobs available in areas that are easy to commute to. Not so with ID. Also, people preferred the other 2 Mountain West states much more. I guess the other major downside is that it has both the largest populations of the 10 states that were considered, and the fastest growing population of the 10 states that were considered.
Looking back at it, obviously, pretty much everyone thought (at least up until this point) it was a bad choice. An organization started (by folks that split from the FSP after the which state vote) to encourage people to move to WY, MT and ID. It was called the Free West Alliance. Of the 3 state branches, the ID branch, if you could call it that, was the least active. In fact, I'd love to see evidence that even a single liberty activist moved to ID as part of it.
http://en.wikipedia.org/wiki/Free_West_Alliance
On the other hand, around 100 moved to WY (though, many of them aren't activists or even liberty folks as neither of those is a requirement for the WY project) as part of the project there and around 1100 moved to NH as part of the FSP. So clearly, up until this point, if you judge by just liberty activists moving, the FWA ID was a complete failure and ID isn't popular at all as a destination for liberty activists.
I know a guy in NH that says he knows of white supremacists that like some aspects of liberty that are moving to northern ID, so I guess ID has that going for it. The top expert that I know of in the Strategic Relocation business claims parts of ID are the best area in the US to move to as for as Strategic Relocation (nothing related to liberty) goes. Though, the same guy says that the Northern NH area and the parts of ME and VT that border it, are the best location in the Northeast for Strategic Relocation so NH does very well (though not as well as ID) in that area, also.