Went by in late June 2005 so info may be out of date but don't think things have changed much.
Loop Road is a good 2-lane road. I pulled through it with a 35' FW and had no problems stopping at any of the pull-offs.
Sage Creek Road was gravel at the time. Very bad wash board so we only ventured down to the first over-look and turned around.
Didn't want to take the time to go crawl since we were headed home from 7 weeks on the road and only had a few more days to get home. Did see enough on the three hour ride down the Loop Road though that Badlands is high on our return list with at least three nights there. Want to spend them out in Sage Creek campground to be as far from anything as possible.
Of course, now with the above mentioned full moon, I can imagine how it would look so now have to add full moon planning into the equation.