I put it all into this chart:
Consider the rest of this article the ALT text for that image. Of the near 13,000 responses, the breakdown was like this:
|I don't like any of them||7%|
|I don't have a preference||2%|
|I've never tried any of them||46%|
From this we can infer that "most" people have tried or currently use a CSS preprocessor (54%). I go back and forth in my thoughts on this number. On one hand it seems a bit low considering how much talk there is about them lately and that this poll represents people that visit and interact with a website named "CSS-Tricks." On the other hand, there is a bit of a uncomfortable legwork involved in getting started using preprocessors. You have to work locally. You need your whole team on board. You have to download and run new software. It's not just opening a text file and editing/saving it like editing regular CSS is. I think it's rather encouraging that 54% of people care enough about their workflow to try this.
We don't know much about the 46% that have never tried it, but I'd speculate it is a split between "I don't need this", "I didn't even know about them", and folks like this: "real men don't need preprocessors."
From here we can get to the meat of the poll: figuring out what the most preferred syntax is. Of the 54% of people that have tried them, 83% of those have a preference. The other 17% either don't like any of them or don't have any particular preference. What we don't know is how many of these folks have actually tried out several of them and chosen the one that works best for them. Surely outside factors influence this. For instance, they are working on a Rails project and Sass comes with it. They like it so they've just stuck with that. Or, they are working on a project using Twitter Bootstrap which is built in LESS. They like it so they've just stuck with that.
Of the folks that have tried preprocessors and have a preference, we can break it down by syntax. LESS is the most popular at 51% of those people. The Sass syntaxes together come to 41%. Stylus is at 6% and Other (e.g. a custom PHP processor) at 2%.
Of the people that prefer Sass, 71% like the scss syntax (more like CSS) and 29% like the sass syntax (whitespace dependent, no braces or semicolons).
It will be interesting to revisit these numbers is a year or two. All polls are archived here. New poll soon.