In the world of application delivery there has long been a choice between reach and fidelity: either your application is high fidelity (eg a rich client with a rich user experience) or it has really broad reach (eg an HTML page). The Nirvana is to bring these two things together so that you get broad reach with a high fidelity application.
And for many years now the Microsoft platform has been one of the few ways - maybe the only way - of getting close to that ideal. Because of the broad use of the Windows platform, applications that are developed for it have very broad reach, and of course they can use all of the power of a locally-installed application.
So where does Microsoft play in this space? I thought it worth spelling out where technologies like WPF, Atlas, XBAP, WPF/E, ASP.NET and WinFX fit in the "reach vs fidelity" world.
Where does this leave us? Simply put, the choice is yours. Where you believe that the Microsoft platform provides sufficient breadth of reach then WinFX - either via click-once install or XBAP - gives you the best possible user experience. Where you need to go broader, you could use Atlas with ASP.NET. And when we start releasing CTPs of WPF/E, you have the option of even higher fidelity broad reach.
WPF/XBAP is an awesome tool for web development. Yet, my company is still forced to use Asp.Net due to WPFs font rendering. When you talk about reach, consider all the people who get headaches from reading WPF's blurry text. I simply won't use a program that has blurry fonts like those found in WPF and silverlight.