As I see the author reads these comments, I'd just like to add that this makes me very excited. C# is my favourite language by far, combining some of the most powerful (mainstream) language features with some of the most powerful dev tools out there.
Having the ability to run the same code in the browser and on the server, in C#, is really a big thing for me.
I think the debugging problem stated in many comments here is overrated: If you're writing an app the size that seriously benefits from the modularity, the tool support and the type checking of a language like C#, you will have a relatively small amount of code directly touching the DOM. All of that other code can be simply unit tested in C#-o-world, straight from the dev environment. If you're writing C#, don't test and debug like it's JS!
Surely such an approach won't catch all bugs and the occasional leaky abstraction (or compiler bug), but it should get one pretty far. Some in-browser unit testing lib together with the fact that the generated JS is quite readable indeed, should help me get the rest of the way.
After the initial curve of getting VC10 configured right, I did an inheritance test. It worked (copied base class prototype, called base constructor with this.) Minutes later I was happily converting C# code to nicely formatted JavaScript. Having spent the last two weeks converting JS to Dart (basically a one way process because you don't want to look at Dart->JS), I'd say this project is a winner and immediately usable. I'm positive there are C# features and libraries that don't convert well, or at all, but I'm not interested in those in the browser any way.
Having the ability to run the same code in the browser and on the server, in C#, is really a big thing for me.
I think the debugging problem stated in many comments here is overrated: If you're writing an app the size that seriously benefits from the modularity, the tool support and the type checking of a language like C#, you will have a relatively small amount of code directly touching the DOM. All of that other code can be simply unit tested in C#-o-world, straight from the dev environment. If you're writing C#, don't test and debug like it's JS!
Surely such an approach won't catch all bugs and the occasional leaky abstraction (or compiler bug), but it should get one pretty far. Some in-browser unit testing lib together with the fact that the generated JS is quite readable indeed, should help me get the rest of the way.
Can't wait to dive in!