node_revision uid -> username

Since not all people would want to name of the person who did the revision, I see no reason to slow their site down by adding one more database query. Just use the user_load() function

  $revised_user = user_load($node->revision_uid); // this loads the user with the given uid into the $revised_user variable
  print $revised_user->name;

This is just pseudo code, it has not been tested, but I see no reason why it wouldn't work. If you have any problems with it let me know.