I'm in shock. Microsoft have decided to remove one of the most useful features in Excel 12 - the ability to synchronize list data. You can still export data from a WSS list into Excel, and you can still publish information from Excel into SharePoint. But what is missing is the ability to synchronize changes between your Excel list and SharePoint.
Microsoft have decided that this feature should now live in MS Access. The only problem is that organisations rarely deploy Access to all their users, where-as Excel is everywhere.
Excel also provides some really nice features for playing around with your data in an ad-hoc way compared to Access.
Read more about this at Bart Bultinck's blog and at the MSDN Excel blog