I'm a developer, and I can tell: porting an iPhone app to Windows Mobile (or Android, or whatever, or the other way around for that matter) is not a trivial task.
Sure, if you have experience with multiplatform development you can make this process much less painful, but it's still far from a simple task.
All points mentioned in the article are moot:
* Language independence: while it's nice to be able to work with any language, it's not such a big deal. Any developer worth their salt should be able to pick up Objective C in a few weeks, and it is a sweet language to work with. I'd love to have garbage collection as on option, thou.
* Working on a single program: while it's true that you use a number or programs to develop for the iPhone, all those programs are very well integrated.
* Licensed libraries: Microsoft licenses additional libraries, Apple has most of these functionality built-in, for free. Some developers are also starting to distribute/sell libraries for iPhone.
* Development tools: iPhone development tools are also built into Apple's tools. For free, BTW. Visual Studio isn't exactly cheap.
* Community: iPhone developer community is huge already, and growing at a scaring pace.
All that said: WinMo (or more importantly, BB) is still an important target for corporate applications, and it's probably worth the effort to port your apps. Just don't expect anything to happen magically.