I'm running the GM on my iPhone 5 and I'm in love. The improvements are huge over iOS 6. I tried beta 6 on my iPad 3 and was less impressed, mostly because it was still very buggy. Read some people's comments on the GM for iPad 3 and much of the same discontent existed: its laggy, buggy, and Apple keeps pulling back on the visual effects (glass blur effect is in some places but not others) but it isn't fixing the lag. I think I will be holding off updating my iPad 3 from iOS 6 until some other folks have tried it.
The question is: Is GM for iPhone 5 the same as the final? Should I still download the final and install it or am I fine just to keep the GM on it? In the past there were no OTA updates from the GM to final.