In Minnesota the good and bad seemed largely associated with who they drove for. The school buses from one commercial outfit were consistently quite good and fortunately these were the bulk of the buses, the ones from another commercial outfit and from a local school district who ran their own buses could be rather awful and I learned to watch out for them. Commuter buses seemed somewhat similar though those who drove for the public MTC could be good or bad. I think most were pretty good but about once per week I'd encounter one who wasn't.