Have you?
Are you saying it’s not necessarily slower to use JS to generate CSS on the client-side, compared to just serving up the CSS with all prefixes included in the first place? Do we really need a test case for that? I’m not even talking about your code or anything; just the general idea.
In general, it’s a bad idea to rely on client-side JavaScript for something that can be done without. PrefixFree is no exception.
I can see how PrefixFree can be useful for quick demos or during presentations (the way you use it is awesome!) but when you’re gonna post an article like this on a site like Smashing Magazine _people are gonna use it_ in production as well.
I love your work Lea, you know I do; I just don’t agree with the philosophy behind this particular project.
Stylesheets are cached and a one-time hit for new visitors - this method has to reiterate on every single page load.