I'm prissy enough about genes to see exactly why people don't like Tay or his family but I seriously did get one of my favorite sims from him too:
http://i.imgur.com/woUAXgi.png
Yeah I know he didn't really get much from dad but he got Tay's mouth, and I think it does illuminate something I see in "ugly" sims: I can't think of any (EA made) infamous ugly sim that has absolutely zero redeeming facial features. Tay has a wide mouth with thin lips but it's hardly something to nitpick over. Faces are mostly inherited by whole parts and sometimes you just have to gamble to isolate a part that's not so bad. Which is still a "prissy about genes" kind of way to word it.
My sim's wishes matter the most in gameplay so if they really want an ugly sim with an awful personality I'll let them at least try it out. They're not programmed to be shallow after all (anyways it's a crime that they didn't bring back turn ons/turn offs and still won't for TS4)