Though Rockstar can usually be trusted to deliever something playable, I'm surprised just how excellent this game is. They seem to have pretty much nailed gameplay mechanics I for one would've thought difficult to incorporate, like duels and the lasso (which is why I didn't preorder it and was on the fence with it even as the glorious reviews started coming out), and there's really no better setting for an open-world game than the endless prarie.
It's like the best parts of GTA4 (many aspects of the gameplay, quality story, engaging and diverse characters) and Oblivion (the incredible sense of freedom and adventure, the beautiful and varied environments) came together in an entirely different (and less commonly seen) setting, and I for one am pretty impressed. For a game that wasn't on my radar at all until a few days before it came out, it sure has proven a very nice surprise. GOTY material for sure.