What I find very interesting about all those rationalistic movements (it's not just Scotland, also Basque country and South Tirol) is that they want to become independent from their current national states, but still want to be member of the European Union. A lot of the promoters of regional independence even want their wanna-be-countries immediately become members of the Euro Area, as far as I know.
I am personally of the opinion that such regionalism (we also see this in Bavaria in a way weaker form) is kinda dumb backward-looking. The national state, in my opinion, is a phase-out model, especially in Europe. But I also think that if most of the people want it so badly, becoming independent, they should get it. You cannot force people to live in a they don't recognize. This never worked in the past and it'll never work in the future.
As for the specific situation in Scotland I cannot say very much about it. The arguing about a possible currency union, however, is interesting, because technically GB cannot forbid Scotland to use the GBP. Scottish banks would have no access to the central bank, but theoretically it could work. Kosovo, for example, does use the Euro as official currency without being a member of the Euro Area.