Whilst my gut instinct would say the same as you, I've seen many very succesful sites that have been around for a long time and are pig ugly.
I think it was Brett that turned me onto Neilson's philosophy of "users don't come to your site to see your content, they come to your site to see their content".
The majority of website visitors (based on seeing members of my community sites' own websites) wouldn't know a "good looking" design if it hit them in the face.
Ultimately, if you find a way to lead them to clicking on what you want them to click on, you potentially reverse Neilsons philosophy. That can be a powerful tool. The same psychology is used by magicians ("pick a card" = "you want to pick *this* card") - I don't see why it couldn't work on the internet.
I think the same applies to copy. I get to see loads of highly succesful online stores with the worst kind of sales drivel you have ever read in your life. I couldn't bring myself to write copy like that. Ever. But these guys actually sell stuff like it's going out of fashion.