I noticed this excellent post by Scott Jamison, an Information Worker architect at Microsoft. He clearly discusses the approach used in Office 2007 for taking SharePoint content offline, which he describes as follows:
Outlook, Groove, and Access each support varying degrees of offline sync with SharePoint, based on the strengths of that application
Note: bolding mine.
I […]

Christian Nordbakk blogged about a new Channel 9 video that shows off the new Excel 2007.
I’m a sucker for slick interfaces and boy did the upcoming Microsoft Excel look fantastic!
If you scroll to ~36:00 minutes into the video, you’ll see some of the robust SharePoint synching that is built right into Excel.