The route is good, and is a very pretty, but somewhat curvy drive. Log trucks and semi's use this road year long, so that and the curves are about the only things to watch out for. Keep an eye out for deer, elk, and moose, especially around sure down.
This is one beautiful drive. I live right off the Montana side of Lolo Pass (Hwy 12) and see large motor homes and some trucks navigate it all the time. If you drive in the evening you may encounter a moose! On the Idaho side at the top of the pass is Lochsa Lodge, good restaurant, forest service campground within walking distance...... river right there too! The road gets less curvy in Montana as you descend towards Lolo but no less scenic. You said you wanted to only drive it once, but you may an insane urge to go rent a sports car or motorcycle and go back over again!
2015 XLR 30FQSL
2010 Dodge 2500 6.7 Cummings
2003 H-D Ultra Classic
25 days out 2016