Yes, you must uninstall the Photoshop CS6 beta before you install the released version. Please see this link for directions on how to uninstall:
Important: Do not attempt to manually uninstall or remove Photoshop CS6 beta by dragging folders to the Recycle Bin (Windows) or Trash (Mac OS). Doing so can cause problems with uninstallation, and installation in the future.
With the Photoshop CS6 beta coming to a close and the 60 day trial period expiring, you'll be looking to uninstall the beta software from your system.
It is recommended that you uninstall the Photoshop CS6 beta prior to installing the official release of Photoshop CS6.
Uninstallation is easy, and can be done in just a couple steps depending on your Operating System.