Jeff Atwood writes about WordPress performance. Quite astonishing – it appears to be that if your blog is medium sized (or bigger) you must install WP-Cache in order it will survive traffic peaks and doesn’t kill your server.
When I read it, my first though was: “too bad they though that fancy control panel is more important the performance.”, but then I though of something else – maybe avoiding performance issues and dealing with other stuff before that, that’s more user targeted thinking of features: most WordPress users are small bloggers (like me (-:) and therefore they need better UI experience than caching, while the big fish can handle the extra hassle of installing WP-Cache or paying for a dedicated server.
Think of that next time you decide which feature to implement first. Remmeber – listen to your users, not your engineers 
Arik