Well as the 'old' adage goes - Content is King.You see many sites out there that look great. It's amazing the innovative designs I've seen out there. Especially - but not only pertaining to - flash sites. But does it help people come to your site. This is your number one goal. Get bums on seats or in website talk get eyes on pages. While it's great to have a nice design it's not completely necessary to getting people to come to your site. You may have the best looking site in the world but what would it matter if no one came to see it!?
Having said that, no one wants to come to a website that looks like it's been eaten by a dog and spat back out. Or a design so simple that your 5 year old could be more creative. When it comes to content people don't want to arrive at your page and have to scroll down because you've written something that compares to War and Peace on your home page. They want relevant, succinct content.
So as a rule KISS (keep it simple stupid) but keep it looking simply great which will make people want to read without being distracted by page that looks like it belongs to the 24th century website art museum.