Here are my thoughts..
1. Looks - This is what draws a lot of people in. And no one wants an ugly snake.
2. Temperament - Not being able to handle your new snake is a big turn off for most people... Be it musking or biting.
3. Size - Some like 'em big and some like 'em small
4. Ease of care/Housing - It <i>should</i> be more important than it seems to be.
5. The "Cool" factor - Some snakes have it and some don't. One of my favorite "uncool" snakes is the Garter Snake. Awesome snake.... just not very cool to most people.
That's what I think is important to most people. Not really what I feel IS most important.