Yet another reason for me to move there!!-
Still trying to talk the MRS into it though...
Unless you are on the Western end, its very flat and very boring (well until the Sioux pop out of the defilades then as Mr. Custer will (well would) tell you not so much.
Now if you have a big boomer that shoots long ways, those open areas are a wonder.
If you don't like the wind blowing you into South Dakota (and one, though the hills around Sioux City may stop you) not a great place.
Did I mention cold? Spent a few hours freezing to death in Spearfish, I needed some daylight to drive thorough the aftermath of a bad snow storm (err Blizzard)