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What difficulties did you face when producing the Saas framework? Also what are your thoughts on CSS preprocessors? Thanks.
That first question is pretty tough to answer. Honestly, one of the hardest things to do in an OSS project is keep your effort up and make sure everyone is getting along. It's working for free, in public, with your personal time. There are great benefits, knowing you are helping the world, but the sheer amount of continuous effort is staggering. I mean, Natalie has been coding pretty consistently on the project for EIGHT years now. I only coded a little in the beginning, but she's just kept it up. Maybe taking 6 months here and there to focus on herself. I think Chris has been doing it for 7 years too!
Burn out is all to easy.
Now, the second question... that's easier to answer. I think they're fine. I use autoprefixer in most of my projects. It's cool.
But, I don't use it for hand-constructing a kind of one-off language with a lot of transformers. The fact that Sass is a stable language to build off of is something I think that's a Good Thing(TM).
Also, I do like the idea they have of exposing the tree for manipulation. That's something we've been looking at in the LibSass/Node-Sass project for a while and postCSS is a great example of why that kind of thing is powerful.