I like the fact that a totally open informational site, with an active community of thousands, and hundreds of introductory pages, can continue to surprise me two weeks after I became an active community member myself and started reading whatever I could about the site.
For instance, Wikipedia supports TeX fontification. Hello? What? My copy of Office XP can’t manage that, but you’re giving me ~real-time equation rendering as I preview updates to any old wikipedia article?
Yep.