"darcs put" (at least) displays "Cleaning pristine cache" and doesn't provide 
actual feedback (i.e. the counters don't increment, or do so only very slowly) 
when, watching its actions on the file system, it's actually applying patches 
to the remote repository.

A guess as to what's going on is that darcs never emitted the final "Cleaning 
pristine cache" message and doesn't emit messages from within "darcs apply" ?

This is easily repeated by putting a repo with a few hundred patches, even if 
the files are small, across a network filesystem.