[sodiumphosphate]

I think it's a good tool. It allows you to produce better code faster. Writing CoffeeScript while reading the resulting JavaScript can probably help you to learn "the good parts" faster. (I'm not saying you shouldn't learn JavaScript 'properly', if you need to deliver a significant quantity of it.)

I've been spending a lot of time writing Boo and reading C#. My intention was to put off learning C# for awhile, at least until after I ship my current project. I'm working on finishing my first game with Unity3D (and quickly developed an aversion to UnityScript).

Boo is an absolute joy to use, btw.

The funny thing is that I'm kind of learning C# by accident, by reading it (and the BCL docs) and writing Boo.

Will I at some point switch to C#? I strongly doubt it. Boo allows me to move much faster, produces cleaner, nicer-looking code, and compiles to equivalent CIL. It's all win, as I see it.