Maybe try to take over the Blackberry space would be better. MS = enterprise; BB = enterprise phone. 10% of a huge market is still a huge opportunity especially if you are making money on both software and hardware.
I have a Lumia 920. Solid phone (that said I'm not a demanding smartphone user). I can check my emails, play videos and podcasts, browse, navigate etc. All the basics. I have no interest in social networks (FB, twitter, pintrest, snapchat etc). If I was and one of those was missing on the platform yeah it would be a deal breaker, but I'm not and I don't. I'm definitely not typical in the developed world that way though I think. But someone with a $10 phone looking for a $50 smartphone in India or China? Might be for them. Especially if what would be a big draw network isn't popular is is even actively blocked from being accessed in their country. Who cares if you can't use FB if no one you know is using it?
Maybe my .Net fanboy showing but as a dev Win Phone is much more attractive to me. Relatively open to devs both in getting stuff into the store, technology stack, lack of 100 "also does" apps in the store already, cross platform support (in the sense of XBox Windows and phone) etc.