I collapsed 2 revisions, that were at the head of my repo (I only use rebase to pull changes). It outputed every single file in the ENTIRE repository to the console command as it did the work. Whats the point of that? It knows what it needs to do. Strip the top two, combine in order, and recommit.
It took like 30 minutes to an hour to finish.
My command was "hg collapse -r 46215:46216" which are the two most recent revision numbers.