[tarwin]

I would not use it for UI work where I want a system style UI, with native components. Something such as Titanium Appcelerator is better for that.

I would not use it to make a website UI, that is for HTML / CSS.

I do use it for games. I do use it for server side programming. I do use it for complex Javascript (including games).

It's write once, deploy smartly. Of course I can't write a server side program and then have it run on my phone, that doesn't even make sense!