I honestly wouldn't have guessed. The layout is understated, the page loads quickly, and it's easy to navigate and read. I wonder if the site is based on some existing content management system, or if it's something custom. It would be kind of a cool surprise if it turned out that Bill authored the site himself for fun (but that seems unlikely).
I think it seems unlikely because we all think of BillG as a business man and not a hacker. Maybe I should only speak for myself, but the thought of him tinkering away into the early morning on his new site is such a wonderful juxtaposition of my image of him.
But remember, Bill Gates started out as a hacker. He spent his whole high school days learning on a computer his Mom's Club purchased for their kids. He says he was probably one of 50 kids in the country that had that much access to a computer in his High School days.
Well he does have a very large interest in the success of technologies still being a large shareholder.
I prefer websites to use silverlight over flash, I think you like silverlight a lot more after using it, even if it is exactly very web friendly.
Silverlight does have some technical advantages over Flash on Windows (eg, event timing in Flash is still tied to frames on the back end), however it's just another old-style proprietary plug in we don't need these days. made even worse by the ghetto OS X and Linux versions.
Flash is the lowest common denominator right now, it's replacement should be HTML video or canvas.
