I would assume that most people out there realized that iOS 5 was released yesterday (Wednesday, October 13). There are plenty of guides out there outlining the new hotness that comes with the update. We have a couple referenced over in our forum.
What is your most favorite features so far? I have really taken a liking to the new notification features. It is pretty slick. Now, I can see all of them that I missed or accidentally skipped as I unlocked my phone out of habit before reading the notification.
Find My Friends looks interesting, but I have not played with it yet. Plus, my wife and I use 4square, so I am not sure it offers much more than that.