Well, if you exclude MonoGame, most of the platform specific code is some window handling (showing messages boxes). The accelerometer, touchpanel, etc... is all handled by MonoGame and even though we contributed to it, it's not technically the core of the flight sim. That's what I counted in the 100% :)

For the UI, it's a custom toolkit we built on our own, so it's 100% similar for both platforms.

I think a lot of the Android fragmentation talk is just fear-mongering in all honesty. If you pick a few flagship Android devices - Galaxy Tab + Motorola Xoom (for tablets) and Samsung S2 + HTC Desire (for phones) - I think you'll be ok. Just make sure you specify which devices are specifically supported and add more as you get feedback. The Android store lets you specifically target certain hardware and over the many years of using an Android phone, I've only had 1 app not work on my phone. I had paid for it, so I refunded the purchase, the app was deleted - no issues :-)

Still, I appreciate the concerns and I also appreciate the desire to implement new features. Bug fixing is no fun. If you do release it for Android though, make sure to post on HN. :-D