I love contact sheets - the story they tell of how you were thinking as you worked, which is often not evident in the selection of the final images and prints. But I confess I don't make them when printing medium format in the darkroom. I like to work straight from viewing the negs.
Weirdly though, I nearly always print digital contact sheets from my digital shoots, using Bridge. These go into my sketchbook, to show my working process (all part of the requirements for the Fine Art degree course I'm doing at the moment).