Hello Everyone
My suggestion is to just keep trying. There's no trick to this. Restarting may or may not help. But one thing is for sure, Apple servers are busy keeping up activating iPhones.
I'm one of the lucky ones that tried for about half an hour and got my phone activated.
It's still a surprise to me that people get frustrated everytime Apple releases an iOS upgrade. If you guys are a long time iPhone user, this should not come as a surprise to you and anticipate the demand. If your phone is something that you use for business or cannot be disconnected for a long time then you should probably waited a day or two for the upgrade.
Just keep trying guys. Best of luck to everyone.