Just came from Eric Rudder's keynote. Office & VSTO were featured in the main keynote demo. Eric Rudder announced the availability of VSTO 2005 SE for download now!
The keynote demo was around software for a fashion company that designed clothing and sells it on the web. As part of the demo, a VSTO 2005 SE add-in loaded into Excel 2007. The add-in provided a custom task pane (app-level) that was used to generate pricing for a garment idustry application. They showed designing the task pane in Visual Studio (with a user control of course) and they dragged and dropped some code to grab pricing information from a web service and put it into Excel. When Excel ran, the task pane was context sensitive and provided information that changed as you moved from row to row in the worksheet. A button on the task pane filled in the spreadsheet with pricing information. A second button submitted the document back to SharePoint to continue the a workflow.
Other key takeaways from the demo: develop applications in Vista using features like WPF and "people near me", use all the cool new features of SharePoint in your apps, start adding AJAX features to your existing ASP.NET applications to make them more interactive, LINQ is still cool and coming in Visual Studio Orcas.
Calls to action: Download VSTO 2005 SE now along with AJAX and .NET 3.0, deploy Office & Vista, start learning about all the new stuff.