It appears that everything from the Wisconsin border to St. Cloud has migrated to, or in the process of, the new digital system. From St. Cloud to Fargo, everything appears to be analog. Eventually, digital will work its way west.
You may want to check the ARMER pages for their schedule.
The 780 is a decent scanner if you are not interested in digital. I have one and still use it for non-digital systems.
If you are going to buy a new scanner, please have a serious conversation with yourself however. If you even remotely suspect you may want to hear the digital systems when they work their way throughout the state, you may as well bite the bullet now, instead of wishing you had, in a couple of years. Their prices have remained constant - even the first generation, (such as the 796) is still what it costs when it first came out, even though a later model has been released. (You'd almost figure an "obsolete" scanner would be sold for a little less, but that's not the case).