I stayed at Glacier Campground this past July and I'd stay there again in a heartbeat. I can't say for sure if it has complete hookups, but I know electricity at my site for a fact. I used their shower facilities which were more than suitable for my needs.
KOA was expensive and it appeared to be more of a parking lot campground that you don't want, but they do have a lot of ammenities. If you want to live on the wild side and stay in a National Park with no hookups, I'd recommend Two Medicine Campground on the east side. About as far removed as you can get, but they have a pretty decent camp store and some decent hiking trails that originate from within the park. We were there 11 days and it by far was one of the best camping experience I've ever had.