> MySQL hogging
That's part of it, but the plain fact is that the style of FUNCTION'crazy/procedural php coding of Wordpress makes for slow executing code. (Especially when compared to zippy straightline/subroutine oriented code of WebmasterWorld's perl code). I would bet the average call to wordpress takes 20-30 times the amount of overhead code that we take here.
You can get around the mysql problems with caching. However, if you are running dynamic served ads or random content, then caching can actually SLOW down your server due to all the calls to produce a disked cached copy of the page. Obviously, you can do some other mem caching with mysql that lesson the hit of mysql, but in the end, there is only so much you can do.
We are going to try some CDN stuff next.