In general, if you have passed a Beta Exam and received a Certificate, you do NOT need to do the Production Exam.
I can think of no situation where this isn't the case. If you pass the beta, there is no need to do the production exam -- period (i.e. not 'in general').
For people taking 'Essentials' exams for OPN reasons (rather than personal ones), there is a reason to take the exam for the current release. The OPN companies gain advantages when a certain number of employees hold the certification for a given version-specific product.
Just to confirm - there is no reason to take the production exam if you've passed the beta. The certifications are exactly the same. There is no designation on your certification that your exam was a beta exam. You've answered the same questions that are on the production exam and your exam was only scored on the items that were selected for the production exam. The long and short is - You are certified and don't need to take the production exam if you passed the beta.