What about this perspective - it's the apps that make the platform. For those who don't use an iPad do you find that you can get all of the apps that you want or need?
From my own experience, clients always want an iOS app, generally want an Android app too, but rarely want a Windows Phone 7 app. Windows 8 Metro (the Windows tablet) is even more of a wait and see. I'll add that there tends to be a lot of excitement around the new Nokia WP7 phones, but not necessarily around WP7 itself. I hear more and more complaints about Android and how chaotic it has gotten and how difficult it is for our clients to keep up with the various versions and carriers. From an app provider perspective they would like to support a clear, consistent path of Android OS versions across all carriers.