As part of working with Node.js I have been using what seems to be the standard template engine Jade, and for the most part it works as expected, however I’m starting to develop a philosophical objection to this sort of technology. One of the promised benefits of using Node.JS is reducing the number of technologies being used on your stack. That means you have to be proficient in fewer technologies in order to built really great stuff. I see CoffeeScript and Jade as completely removing that benefit.
If you use them, you now have to be intimately familiar with their syntax and idiosyncrasies in addition to the underlying script / markup that they get transformed into. It’s not like you’re replacing Javascript with CoffeeScript. If you have to debug anything, you now have to understand both the Javascript and the CoffeeScript in order to try to figure out where things are going wrong. The same with Jade. If you see a problem in the html, it’s not a simple matter of changing the html. You have to mentally convert from html to Jade syntax in order to fix the problem. I see these frameworks as adding a lot of additional complexity when debugging problems for the very short term gain of typing fewer characters.
No one would use C# if you have to be an expert at CIL to debug it! The tools are good enough that you can happily write and debug C# for years without even knowing that there is a CIL and until Jade and CoffeeScript get to that point, they will be more trouble than they are worth.