hg archive "only files modified/created in this revision" seems to give an incomplete export of affected files.
I've had this a few times, but looks a little inconsequential to me. When I merge a changeset into a repository (both have the same branch), and i export only the affected files, those from the pulled branch wchich are only updated ("<--" arrow in the files list) are left out. This complicates the workflow a bit for me, as I usually need all files changed by the revision.
with best regards