Been running the latest beta (4) for a few days now. To install:
Step 1: Restore your Device to 5.1.1.
Step 2: Select "Check for Update" in iTunes while holding the Shift button
Step 3: Select iOS 6 firmware and allow it to update phone.
nb. Save you shsh incase you want to downgrade in the future.
My phone is factory unlocked so if you need to use ultrasn0w for unlock do not upgrade to ios 6.