One of the common complaints regarding Microsoft is that the company has problems eating its own dog food. Even though it promoted Windows Presentation Foundation as the
programming framework for building Windows and web applications, it so far failed to produce any significant WPF applications itself. None of Microsoft's major applications use WPF (Expression Design and Blend aren't major), which does not help in promoting it as the Next Big Thing. This may all change in the near future, as a small but extremely popular Microsoft application is about to make the switch
to Windows Presentation Foundation:
Windows Live Messenger.
Since there often seems to be some misunderstanding as to what WPF exactly entails, I will let Wikipedia explain what WPF is.
The Windows Presentation Foundation (or WPF), formerly code-named Avalon, is a graphical subsystem in .NET Framework 3.0 (formerly called WinFX) and is directly related to XAML. Version 3.0 of WPF is pre-installed in Windows Vista, the latest version of the Microsoft Windows operating system. WPF is also available for installation on Windows XP SP2 and Windows Server 2003. It provides a consistent programming model for building applications and provides a clear separation between the UI and the business logic. A WPF application can be deployed on the desktop or hosted in a web browser. It also enables rich control, design, and development of the visual aspects of Windows programs. It aims to unify a host of application services: user interface, 2D and 3D drawing, fixed and adaptive documents, advanced typography, vector graphics, raster graphics, animation, data binding, audio and video.
While WPF was generally well-received, nobody, apart from Yahoo!, seems to be using it for any major applications. The consequence of this is that users do not encounter WPF-based applications, which in turn leads to lack of demand from users - you don't miss what you don't know. When Apple introduces a new graphical framework (Core Animation, for instance) or a new programming environment or whatever, Apple will use it in major applications, which in turn leads to other programmers adopting these elements. This isn't happening with WPF, and it seems like Microsoft may finally be willing to start eating its own dog food.
As Messenger Stuff claims:
After being tipped off by an unaffiliated yet trustworthy source who – naturally – doesn't want to be identified, Messenger Stuff can now reveal that the new interface will use the graphics effects available through WPF where supported (i.e. on Vista and with a decent graphics card).
While Messenger may be seen as a minor application, it does get deployed on many, many computers. In The Netherlands, for instance, Microsoft's messenger service controls round and about 99.9% of the market, in such a way that "MSN'en" has become the verb for instant messaging. Windows Live Messenger might very well be a nice way for Microsoft to dip its toes into the WPF water.