just returned from L & C (St. Louis MO to Havre MT).
What can I say? It all depends on the temperatures and the winds. There were days when I cursed it all and rather would have joined L & C in 1804, days when I loved it and thought, poor L & C didn't have bikes with them and far more often I just loved it). Might sound strange, but I did like the parts riding on the Interstate (rest areas every now and then and I could rest in the shade of overpasses). You are well advised to start in Pierre, no offence meant against Iowa and Nebraska, but sometimes cornfield right and cornfield left for miles and days and no shade is not so exciting.
Liked very much the city parks for camping, mostly with a swimming pool nearby (Pierre with nice swimming in the Missouri, Circle MT, Harlem MT and other places). A detour from Malta MT to Zortman in the Little Rocks is definetely worth while, Fort Peck wasn't so exciting (unless you are dam freak).
All in all, even with the heat (2 weeks with 100+ after noon) and the headwinds (ideal for loosing weight), with the landscapes (prairie in the Dakotas and endless skies in Montana and the ever so helpful and friendly people, it was a great experience that I wouldn't want to miss.
Oh yes, the Williston nightmare seems now to reach places like Dickinson MT (the campground doesn't allow tent camping any more and the cheapest motel I found charged 98 $, but nice breakfast buffet). So prepare for adversities (but the heat wave is over anyway), take your time, be patient with nature and yourself, watch the beetle that wants to cross the road.
Have a good trip.