I run my Nook Color with Cyanogen and the Nook app for Android. I think I may miss in-store promos or things like that, but, in turn, my browser experience is much better. And it also runs the Kindle software.

There already is Nook software for iOS and Android (and, most likely, Windows and OSX). I don't see how the heir to WP7's market share can even move the needle here.