Played an hour or so and it has not dissapointed. Horse riding takes a little getting used to but they look amazing in action. You can also shoot just about anything that moves including birds flying way overhead. I thought it might be a bit too much like GTA but that isn't the case. Has it's own distinct flavor.
Just one example of the neat stuff you can do.
http://www.liveleak.com/view?i=468_1274045745