Unfortunately, I have to say, Jakob has perhaps the worst site design I have ever seen. It is as if, while he is handing out the Oscars, he is wearing a plaid polyester suit. In truth his site is fine from an information architecture perspective. But from an aesthetics perspective it is awful. And aesthetics is important in UI. If you begin to look at something and want to avert your eyes, the site has failed.
I could make mine every word of this blog post by Hank Williams (found via Daring Fireball), especially the funny quote that you could read above. I also do respect the work of Jakob Nielsen, despite the ugliness of his site and the funny corporate pictures on it.
The point is still, the layout and typography of your site do have an impact on its usability. The alertbox is a good example of an unreadable webpage, a huge list with no spacing whatsoever that makes the page confusing. Makes me wonder if our usability doctor has made any usability test on his own website…