This weekend I worked on my first extension for Brackets - CSSLint. The experience was pretty interesting. Much like writing extensions for ColdFusion Builder, your time is split between creating the UI/extension connection points and the actual logic of the extension itself. In this case, since it was my first extension, I'd say 95% of was on the "Extension" aspect and the rest on running CSSLint. Which is to be expected I think. The CSSLint tool is trivial to implement in code. In fact, once I got the current document in Brackets I just had to do this:
results = CSSLint.verify(text);
Here's a quick screen shot of the results. If you are curious - it was run on a file from jQuery UI.
Here's a shot showing a complete view of Brackets and my extension running:
If you are playing around with Brackets, you can download the extension and give it a shot. Let me know what you think.