Well, as long as FOG isn’t finished yet (still beta), it’s probably smart to upgrade FOG whenever you can, due to solved stability issues in newer versions. Especially when using FOG in a professional environment. But that’s just my opinion.
I don’t really know what has been updated in 0.31 and 0.32. You should read the [URL=‘http://www.fogproject.org/wiki/index.php/Main_Page’]release notes[/URL].