Well I threw caution to the wind and upgraded the MoveableType version for my blog. On paper it's a fairly painless process - just copy the new files over the old ones and run a script to do the update. In reality, it's several hours of work and frustration to figure out why the copy didn't work, and why the script is generating errors. Then there is the fear factor that the script will wipe out all of the old posts and pictures so an extra hour or so taking a backup is involved.
For the most part, we shouldn't see an major changes if I've done the work correctly. If my blog goes down for several days then you can assume the worst - LOL.