Attractiveness is obviously a subjective thing to measure, but so is intelligence. Measuring IQ is an effort to do this and asking people to rate someone's looks is similarly an effort to measure attractiveness.
As for the stereotypes, first of all, I bet Johnny Depp or Brad Pitt would look a lot worse if they also suffered from ALS and were at Hawking's age and vice versa, Hawking would look a lot more attractive if he was healthy and had trained professionals deal with his appearance all the time.
Second, being a cheerleader doesn't automatically qualify you as a bimbo (though I don't consider it the smartest choice to participate in one the riskiest athletic activities around), neither does not being a cheerleader qualify you as non-attractive - I know for a fact there are tons of attractive girls who would never want to become cheerleaders.
Honestly, the "ugly but smart" stereotype is one I never quite understood. Even judging from IQ, when you see people with very high scores, rarely do you find any who would score low in the attractiveness department. Similarly, people with very low scores usually give out a bad visual image, as well - go to asylums, mental hospitals, you aren't finding lots of attractive people. Want less extreme examples? Take hard labor jobs, manual jobs and most jobs that don't require any decent intelligence. You're not likely to find lots of people to be physically attracted to. Go to prisons, the vast majority of prisoners are physically plain ugly, and though there are some highly smart criminals (and even they are usually not the unattractive ones), the average prisoner is definitely a below average intelligence person.
All the afore-mentioned are stereotypes as well, but they are more substantiated than the "smart & ugly" and "beautiful and dumb" ones.
Oh, and for the title of the smartest poster in the board, at least among the ones I've known a little bit, Tharegul8r is my choice - his experience helps as well, but still I've not met many people with his experience with a similar level of intelligence.
I don't post much in the OTC, so I don't even know half the posters you listed, but if I had to pick a guy from the main forums it would be KnoeItawl. In fact he seems like your typical overly-intelligent asshole. You can tell the guy is a genius but he also comes off as bat shit crazy.