WP has the best keyboard across all platforms, why would you want to install anything else? i can understand the need for different browsers but microsoft is addressing that with the next major upgrade.
my issue with android is that there is no design coherency between 1st party apps and 3rd party apps. they are pushing developers to follow a design language now but they are behind microsoft in this area. you'll find most 3rd party apps for WP using metro; it creates a great user experience.
Gizmodo Has an interesting interview with Sam Moreau of Microsoft's design guru. There are other things about the Windows 8 design in here but there's some WP tidbits too.
Quote
Giz: Right, when I talk to people about Windows Phone, some people don't like the cutoff text or whatever. But it has a sense of vision—a really strong sense of vision—and I think that's a good thing, one way or another.
SM: Yeah, because that was the thing that we get blamed for a lot. Or, I would say the thing that annoys me about Android is I don't think it has a point of view. I think it's trying to be this weird sci-fi version of an Apple design language, poorly executed. Some of it is starting to get there, you know, they got Matias there, and some things are starting to get a little better. They're starting to get that—some sense of soul, but I do think that a lot of their soul is derived from some other place.