Badlands Inn is where we opted to spend 2 nights while at Badlands National Park. We had two rooms there - and found adequate accommodations with air conditioning, a great view, wonderful proximity to the park, and a very friendly staff. We had reservations a few months in advance - and suspect they may have been needed as there are only 18 rooms here (all non-smoking).
Other than Cedar Pass Lodge (which is run by the same company and was already booked by the time we made reservations), Badlands Inn is the closest you can stay to the National Park. It is located just south of the Interior Entrance (located off the Rt 240 loop road - take Rt 377 towards Interior). The view of the Badlands is simply gorgeous - a wonderful way to wake up - and end your day.
As a note to folks, by staying here you are staying well away from "civilization" (meaning restaurants, shops, etc). This is a plus for us, but might turn others off. If you like civilization, look at staying in Wall. You'll pay more (that's where we stayed 2 years ago), but you are "in" it's all there.
There is no pool at this Inn, no restaurant, and no gift shop. It's a place to stay with comfy bedding, nice air conditioning, and a wonderful view. It does have satellite TV, telephones and coffee pots in the rooms - for those who need them. Choose for yourself if this is what suits you. We'd stay there again.