Especially for reference sites, I'm generally a fan of spare UI designs with plenty of white space, but the most important thing to me is utility, and that includes speed.  A fast site that helps me find the right information quickly beats anything else.

Your comment about academia, serif fonts, and karma is interesting.  I've always wanted to bring Scheme out of academia and make it attractive for real-world use.  The language has stellar academic roots, but I've sometimes worried that they hold it back.  So I would evaluate a font based on readability, not worrying at all about making it look more academic.