archive imports

I get asked every once in a while about importing an existing archives
for a list. Curently the import mechanism is fairly painful and highly
discouraged on our FAQ. I'm now interested in taking a look at this
and seeing if we can do a better job. Does anyone want to volunteer
for being a guinea pig?  

Specifically, I want someone who wants to "backfill" their archive,
who has their raw messages in one of the following formats or
protocols: mbox, maildir, MH, IMAP.

Cheers,
Jeff