Much more than just Grand Theft Equine!
On the surface, it would appear this game must be very similar to GTA IV. In terms of control, graphics and storyline, it really is. But it also features the best things of San Andreas: Entertaining distractions. Between the hunting, the card games, loads of in-game achievements and the brilliance of random events, its easy to play Red Dead for hours and not move the story forward.
The random events provide a level of realism and immersion to the game. As you explore the world, you will come across people in need of help, gangs of outlaws, trigger happy sharpshooters looking to duel, escaped convicts on the run and much, much more. It goes a long way to creating the feeling of the old West.
Some minor glitches will intrude from time to time.. Also, the same problem that exists in every Rockstar game, auto target priority, is present. The game is unable to determine if the high priority target is the guy shooting you or the bird flying over your head. Its not something that comes into play very often, but in the right situation it can force you to reaim, or cause you to blast your horse in the face (hilarious btw!) The difficulty is also absent until the final 1/4 of the game, and even then its still not quite up the level of GTA's tougher moments.
Overall, the game is stunning. Its well written, if a bit predictable. It controls smooth, the horses are fun, but they lack the variety that you get from automobiles in GTA. I can't really think of a reason for you to not play this game. Its pure fun and a further step in Rockstar's highly refined formula. Just don't expect perfection. Sandbox games are always going to have their small blemishes. Its not an issue when the core gameplay is solid and the sandbox is both beautiful and thrilling.