I don't have it yet but it looks incredible.
There was a pre-order deal and you got a special code you could redeem for a pair of golden guns or something like that. I heard people are putting their codes up for sale on ebay and getting almost the price of the game for it.
TIP:
first thing...
go to options, change your camera view to "camera relative" from "horse relative".
it will save you some frustration when you have to look at things while riding.