[pulledpork]

I've created dozens of sites and never really noticed any CSS performance issues.

I have got orders of magnitude faster sites by combining CSS or js files, gzipping content, adding cache control headers, serving via a cdn and not serving code that's not used.

I've also really benefitted from using logical markup and CSS selectors, not those designed for "efficiency" of the computer rendering them.

[Schlaefer]

If you are done with the obvious optimizations, at some point you spend half a day to gain 50 ms on the backend. And that's a good day. If you are able to achieve 25 ms on the frontend in half an hour, it's worth considering. E.g. Font Awesome [1] is very popular, but the selector performance is horrible.

[1] http://fortawesome.github.com/Font-Awesome/