You're right. It's not like we weren't aware of making these mistakes, we were so clouded and close to the project that you become blind to them. You need to force your way out of that...
One of the ways we've used in the past is that FeedbackArmy service. For $7 or whatever, it's a great way to ask a few questions like "What does this site do?" to a lot of random folks you'll never know or see.
