Via the US ISV Developer Team Blog
Microsoft Office 2007 SP1 will be available for download Dec 11. The improvements in 2007 Office System SP1 are in response to direct feedback from power users at large organizations or indirect feedback from home and Office users through the Dr. Watson bug-reporting system.
I haven’t seen any details about what’s been done, but don’t expect any UI changes or charting improvements. They might have fixed some stuff, buy I’m not getting my hopes up.