I've been taking a different approach for the last few years, building apps in MOAI, which is basically "like Java, but you get to/have to be a native host developer as well".
MOAI is a cross-platform Game-engine/GUI-toolkit designed tot allow pretty fast depiction of games/GUI interfaces, specifically game-like interfaces. It is very easy to get a working game environment, of most of the most common forms, in 20 or 30 lines of code in MOAI, i.e. Pong, jump'n'run, shooter, etc.
On top of that, there are already 3rd-party frameworks which implement some sets of standardized "GUI" basics like sliders and buttons and scrolling scenes, and so on. So its possible to do a common GUI that runs exactly the same on all platforms - i.e. ignore native entirely and boldly forge ones own ecosystem of standards.
Which is actually kind of nice, to be honest.
So I'm wondering about the C4 side of things and your plans to embrace/wrap/extend the GUI world. Will you be a subscriber to the native world - and thus either have to do a lot of native host code (or find some way to make your developer-users responsible for the problem) - or do you think there is a future in non-native/runs-everywhere GUI development beyond that provided 'by the majors'?
I'm going to put C4 on the lab-bench some time in the next few days, looking forward to checking it out ..