A HUGE HUGE thank you to Carthik who made a fix to the current import-mt for me because of some issues I had when I imported my MT entries. (I've since deleted all the imported entries – and used his new version to re-import them and now everything is beautiful again!) 😀
The only drawback is that any "new" comments/trackbacks on those old posts have been lost. I apologize for the inconvenience of that. I don't think there were all that many. It was either that or have two years worth of scripts be very messed up.
Until the fix is included in a specific release – here is the fixed import-mt.php that Carthik sent me.