I get where Andrew is coming from here. Zappos' website feels insanely old and I'm sure many people get turned away because of the design and never get a chance to know how awesome zappos as a company really is.
ie. My mom would sign up for Facebook.com before she touched MySpace, even if she didn't know the difference between them, just because of the better facebook design and execution on the sign-up page.
On the other hand, they're really well known and continue to grow and what the majority of you are arguing is 'why touch it if it works?' Which is the wrong way to look at it. You should be asking 'how can I make this a better experience for my customers?'
Keep in mind also that the Apple Store sucks at discoverability for non-Apple products - Apple does a marvellous job funnelling you towards the MacBooks and iPods, but a poor job exposing, say, third-party accessories. This works great for Apple, but would be instant death for a company whose entire bread and butter is selling third party goods.
Now consider that Apple has how many core products? What you see on the root store page is it. Everything Apple makes and sells is right there. Now compare with how many products Zappos is in charge of selling and you start seeing the scale difference.
You are comparing apples (no pun intended) and oranges.