Web based applications makes a lot of sense for some tasks, such as addressbooks, managing your books, simple databases etc... The reason is that you can design a very usable interface using HTML which is not easy with WebForms. For example, Outlook is
a powerful program, but its interface is worse than say gmail. For many people, the simplicity of that interface is the key point. In other words, the point is to write apps using the web interface and for that you definitely need a web server. With web servers
you can have all sorts of useful applications. The reason we don't see such useful applications is mostly because you can sell those apps to home users. Even though XP Pro comes with IIS, the user has to install it expllicitly. However, we see people writing
these applications for intranet or the web itself. The best example for the type of applications I am talking about check out Userland's Radio blog software which is a single web server and a blog application. They use the browser to interact with the user.
I do think that Windows will gain a lot of appeal for such applications. The only possible downside to Microsoft might be the fact that this move will put more empahsize to the web applications which normally you can run in any platform.