I think that by fixing common problems before launching, you get more meaningful feedback later from your users. They won't concentrate on the obvious problems that could have easily been fixed.
But failing to launch of a month while you 'polish' things will make a difference. You'll lose out on feedback, potential customers, and give more foothold to any competition. Plus it's boring and expensive to not launch.
People who'll walk away because there's a spelling mistake on the contact page would never become paying users regardless of how great your product is. Ignore those people.