The C# code uses readonly to produce the immutability provided by F# by default. This is why they use full properties. However one can argue that C# does not depend on immutability as much as F# does so you won't write it like this anyway.
Guys you totally skipped the cool part of the XNA Starter Kit port. It is not a guide how to port XNA games to the web. It is a TOOL that compiles IL (as opposed to C# in Script#) code to JS and he's ported the XNA Starter Kit as a proof of concept. Your review fails to convey the total awesomeness of this announcement.
As for the Win 8 announcement they'd better not wait for september because the Windows devs are in rage right now because JS and HTML were mentioned and not .NET.
@Mario:No it does not mean that... You can use whatever you want on the server but your UI will be HTML and JS whch sux. You can use whatever technology you like for a backend of your Windows Forms/WPF app but you don't need to build the UI in stinking HTML. However I don't expect a web developer to get it. As a web developer I work with web developers and I know that I don't want web developers developing the desktop apps I use as a user.
@Michael Butler:But of course I will use .NET as the backend for my Mono on Mac, MonoTouch and MonoDroid applications and also for every platform I can develop for in non-web technologies because I hate them:)
Even if for some reason MS believes JS and HTML is the right way to develop windows stuff (ha ha!) They'd better make sure there is not a single piece of Windows that cannot be developed using WPF/SL. Otherwise they will face the developers' RAGE. Remember the "our SL strategy has shifted" fiasco? Like this only much worse. Maybe some web guys will be happy to hear about HTML and JS in Windows but they don't like MS. They won't develop for Windows even if they could. Does MS really want to use the dedicated Windows devs?
BTW I am an ASP.NET Web dev and I hate the web bullshit with passion. As a user I hate it even more.