The whole "Apple is being a jerk to developers and iPhone users to the point that the US Government has to step in" situation has given one of their potentially greatest threats an opening salvo in the smartphone application wars.
Microsoft's Windows Mobile Blog has written an informative and helpful article for developers about porting iPhone applications to the Windows Marketplace. Using a case study, it features developer Luke Thompson's experience in converting his Amplitude application from an iPhone App to a Windows Mobile one.
The article talks about the relative ease in porting the application using developer-friendly tools such as Visual Studio 2008 by Microsoft and by reading helpful programing sites like Code Gallery and The Code Project. It also took a quick jab at Apple by talking about how the iPhone does not allow applications to run in the background (apps are closed when you exit them) while Microsoft requires it.
You can follow Luke's porting journey here.
Windows Mobile Blog - Ready To Port Your iPhone App to Windows Mobile?