Hmmm, most of these new features seems complete new to me.
Generics must be the C++ equivelant for function templates, right? You can save some typing, but nothing more. Really, besides the max and min functions where else can I use it? I'd prefer to rewrite some code.
Oxygene's await keyword and nested classes...., well, I don't know what are these, really!
For..in loops. Come on, this is javascript, not pascal! Besides I'm trying not to use for loops at all, instead I like writing while loops using for the exit-loop-contition some pointer checking (perhaps a bit faster code).
final methods: Unfortunatelly I don't know what's this.

Even when I'm using forms, not only in games, I'm trying to stay 'procedural", without using objects/classes. Also as an old school programmer I 'm not used to some newer features. The only, let's say, year 2000 era feature I'm using are the optional parameters with default values.