Oddly, I gave this plugin a try on two copies of the database -- one, a backup I had from the most recent import (which brought on the dreaded encoding problems), the other a nearly identical database with some posts over the last week.
On one copy of the database, it worked perfectly!
But on the live site (with the additional posts), it had the effect of truncating all the posts. Have you seen anything that would cause that?
I'm coming from an old WP database that was latin1 / swedish ci.