You need to TEST it. and TEST IT and TEST IT SOME MORE.
I would suggest a PRIVATE BETA testing rather than a PUBLIC BETA testing.
Gather a few of your friends, family members, grandma, grandpa and tell them to try it and give you feedback.
Their feedback will be better than nothing.
But a real tester will really try to make your site crash, do different kinds of conditions (say incorrect zip code, or missing fields), or do SQL injection (to hack your site) and see if your site will stand up to public use.
Then there's also load testing. How many users can your web server handle. If you have a database, are your tables indexed properly for the fastest performance, etc...