While looks factor in the least for me, they are the first thing I notice. Sometimes I can see someone who looks beautiful, and my first thoughts are that I hope she's sweet and funny. Looks do play a role, I would be lying if I said they didn't, but someone's personality changes my perception of their physical appearance.
The old adage is true that beauty is skin deep and ugly goes straight to the bone, it's just that it doesn't quite work the same way others may use it. I become attracted to people who are very human, and in the process, I often bypass what they look like on the outside. So suppose someone who looked like, say, Salma Hayek, were to ask me out on a date. I'd be VERY interested, but if she had terrible personality traits, I would find her to be quite ugly.
Now that I think about it, I'm pretty certain there was a movie based on this idea.