[blntechie]

As a Windows phone user myself, I will be happy if you can support IE. I am not asking you to make decisions based on IE support but if you can support IE with only little tweaks to your iPhone/Andoid codebase, I would recommend you to do that. If it works in desktop IE9 it will work in mobile IE9.

[gsmaverick]

I've had some experience with trying to make things that work on iOS/Android work on WP7 and it's nearly impossible. For starters mobile IE does not implement tap/touch handlers; which is a dealbreaker for mobile web apps.