[brucehart]

I would recommend developing your code base using Qt, which will export to Android and iOS. I think Windows Phone will be supported in the future, but has not been fully released yet. Qt is open source and free to use under LGPL.

[roberjo]

I have seen some really good things about Qt.

Are there any user paradigms that work better for Qt? For instance, CoronaSDK really excells at game development.

[brucehart]

There are a wide range of modules in the Qt library including an OpenGL library if you want to do 3D games. I would say that Qt is strongest in doing basic apps with standard components like buttons, images, sliders, etc. since there is a large built-in library of Qt widgets to use. The down sides are that your apps may not look 100% native and the Qt libraries add a few MB of bloat to your app size.