For a more detailed overview of what's under the bonnet on Mac Office 2008 then please visit this site. It has some great graphics of the new release plus access to the Mactopia newsletter.
The official release for Mac Office 2008 will be/was at Macworld where you can join in if you're lucky enough to be over there.
I know of one university that has been on the beta for Mac Office 2008 and is ready to start installing the final release once they're able to get hold of it. IMHO one of the main features of this new release is that it is all about re-connecting users with the power of Office. As well as this, there are some significant updates to the components in the suite which should impress.
I'm not a Mac user but I look forward to having a tour of Mac Office 2008 with friends that are, and I'm sure they'll give me their opinion of the new version.