I'm using these to teach an intermediate mechanics class, and my only regret is that there are no problems. The flip side is that sometimes Feynman skips over the derivations of certain things, and that makes good assignments ("Fill in the steps between [these assumptions] and [this result]").

Feynman's writing of course is stellar. The order is a bit unusual and not really designed for a "standard" university-level course. I can pick and choose, but I wish I could easily reorder the material.