Just sold my Macbook Pro a few weeks ago, and built a windows 8.1 gaming desktop. I am VERY excited for Windows 10. I think Microsoft has something really good going on with these announcements. That being said, I don't think I will be exchanging my iPhone 6+ for a Windows phone anytime soon. If Microsoft reaches parity in the app category, with either major platform (Android, or IOS) I may think about it.
Windows phone as a desktop, could be a really cool feature, hopefully it's not marred by slow performance issues.
Would have to think they are going to have to get away from making so many lower end phones if they plan on making the phone as a desktop feature appealing.