Bruce,
Some have reported workspace corruptions in M060. M061 is supposed to fix it but the same people report it does not. That all being said, we migrated to Ilink M060 & WF4.0 in fall 2008 with no problems at all. No workspace corruptions & everything works fine. Personally I would not let these possible problems hold up your migration. Knowing it could happen requires encouraging regular check-in of modified objects, at the very least daily, which is best practice anyhow.
I've recovered files from corrupted workspaces before & it's not that hard although I've never had to do a really large amount of files. The import function seems to work well in M060.
Regards, Joe S.