I evaluated CS but ended up using Script# in my latest project at my day job, mainly because we are Microsoft shop and it will be easier for other C# developers to jump in if the need arises without learning a new syntax.
Trying to use a language that's vastly different to JavaScript to compile to JavaScript is an impedance mismatch that is destined to create more problems than it solves.
So far I’ve been very happy with how the project is turning out and I already see a lot of productivity gains; there seems to be much less run/test/debug cycles. The tooling/intellisense is so much better than the plain JavaScript and a lot of the typos and errors are caught at the compile time. Plus, writing C# on client and server is such a nice change.
Anyway, CS would be my second choice but that’s just because I work in .NET environment.
