I mentioned the Office Developer Conference in a previous post due to its relevance to Smart Client applications. In the Bill Gates keynote, you will find references to Office as a platform and a demo of the Visual Studio for Office 2005 (VSTO) product which I have a personal interest and pride in. The ability to utilize the full functionality of a robust spreadsheet application like Excel and extend the application through customizations (Hosted .Net code) is a major pillar in the Smart Client paradigm. Imagine the development opportunities in extending an existing robust application as opposed to starting with an empty Winform shell.
Video of the Bill Gates Office Developer keynote.