I know I have covered this off, but just check it out again and found that this update had snuck in! Maybe we will get the full details ..eventually!
This service pack also fixes the following issues.
Note These fixes were not previously released in a rollup package.
939471 The text of the e-mail message may be corrupted when Exchange 2007 receives an e-mail message that does not specify character set information
946641 How to change the method for transfer encoding after you apply Exchange 2007 S946641 to the Exchange 2007-based server that is running the Hub Transport role