I got it primarily for the "assault weapons" purchasing. I think that they were going more off of my place of residence over the last two years which is listed on the forms. The lady that I delt with was more concerned with that. Right now I am not looking to purchase a handgun, just a lower receiver in MN. Therefore the interstae GCA restrictions on handgun transactions don't really apply to me right now.
My permit has my current MN address on it, and if I got a MN ID I would have the same address on that one. The MN DNR accepts the ID's as acceptable proof or residency as far as purchasing licences and such is concerned, and it seems as if an ID is concurrent with the drivers licence with proving residency. I'm not going to switch drivers licences since that would cause problems with insurance and my CDL.
I havn't found any MN statute that prohibits a non-resident from purchasing a handgun in another state, but the GCA regulates such transactions. You must prove that you "make a home" in a particular state, so a MN ID should satisfy that.