Netflix, for one, offers an app for Windows Phone and for the iPhone, but not for Android. Why? Windows and the iPhone offer a common security platform across their devices, meaning that Netflix can develop a single app for all models. Because Android is implemented in so many different ways, however, Netflix has been forced to create specific versions for each phone, which has slowed down its Android development.
I still see Windows Phone 7 as an appealing platform for developers, if the reach is there. It’s a big and complicated “if” because even with all the advertising dollars spent, the distribution is still absent. In fact, I don’t know a single person that isn’t a developer who has a WP 7.
Providing a strong development platform only matters inasmuch as there being a strong financial incentive to develop for it. And for that to happen, WP 7 devices need to be in many more pockets.