Hi Earle:
Pretesting is good for benchmarking. And your other uses will be usefull too.
I like to compare beginnig of class to end of class performance to see how far the students have come, and also, sometimes, used as a guage of my teaching effectiveness.
I don't do pretesting all the time. It can be helpful when I'm unsure what level the new students are oiperatin at overall, as a group.
Regards, Barry