A good idea, but I have a long-standing ad setup with Ad-minister. When I replaced that plugin with the modified version — and made a single change in the contents of one ad block, it messed up our entire theme, putting all ads and text in the wrong place. Reverting to Ad-minister didn't work; I had to restore from a previous database backup.
So I'm hopeful for this new version, but it has a ways to go. You need to be able to read the old data without messing up things once something is changed in an ad.