The post talks about Windows phone and the features that it offers. It does a good job of comparing the Windows phone platform with the Google's Android and Apple's iOS mobile platforms.
On an iPhone, the walled garden approach works well because people are familiar with iTunes sync and know how to get their stuff onto the device. Everything is tied to the iTunes account, and the addition of iCloud makes things easier.
On an Android device, Google takes care of everything. Pop in your account information and everything just works. You've got your email, contacts, calendar, picasa, youtube, and voicemail (google voice) all tied to one account with a simple one step setup. The UI falls short of iOS in some cases, but the users sacrifice that for flexibility.
On WinMo you've got your Windows Live account, but to me it's always felt like Microsoft is loosely coupling random services together. While I can use one account, it doesn't feel as integrated as it does on the other platforms, so I don't use it. That's the problem. It's nothing wrong with the phone, in fact, I'm sure it's completely seamless on the phone. But they make zero case for me to migrate from Google to Windows Live, which is a huge thing to do in this day and age. Those services just don't compare to Google's, so why would I switch just for the phone? In addition to that, I don't feel that they've done a good job of fostering developers over to the platform (which seems excellent, based on the code and examples I've seen). I don't think they can fix that without first convincing the users that they need WinMo, which means they need to convince them they want/need Windows Live. If Microsoft can improve Windows Live and make it a viable competitor to Google, then they might have a shot.