Since Windows Phone 7 Series is a brand new operating system, old apps won't work on it (unless it comes with some type of legacy-mode or unless a third party builds an app for "classic" Windows Mobile). In any case, I'm predicting that apps will simply need to be rebuilt. It's really a shame that Microsoft didn't make this move a few years ago. Now, they're faced up against the Apple iPhone, RIM BlackBerry, and Google Android operating systems. I forgot to mention that Palm still has webOS and Nokia is tied to Symbian, but no one I speak to seems to be very optimistic about the future of these smartphone operating systems.
So, what will Microsoft do to make Windows Phone 7 Series a real winner? I'm really not sure that they can do anything. Maybe their smartphones will be free. Maybe the data plans for these devices will cost significantly less. Unless there's a major motivator for consumers, I think that most will simply choose either the iPhone or Android. Business users will still be drawn to BlackBerry, but that trend may evolve as iPhone and Android gain more users on the corporate side. In the world of health care, the major issue revolves around medical apps. I doubt that Windows Phone 7 Series will offer any type of unique medical app that can't be found on any other smartphone.
At the end of the day, I think Microsoft will have a really difficult time catching up to iPhone and Android in the health care sector. Let's see what they may have up their sleeves as new smartphones start appearing with Windows Phone 7 Series.