IGN recently got a chance to sit down and watch Red Dead Redemption being played. We've extracted the most important points below.

• Open World
• Along with San Digeo, Rockstar North and Rockstar Leeds are also working on the game
• Uses Euphoria
• At the beginning of the game, things from John's past come back and force him away from home and in to the wild
• Players will be able to accept missions, engage in mini-games, ride horses, trains and stagecoaches, hunt and go on killing sprees as they wish.
• The world is divided up into three large sections: Frontier, Mexico and Northern territories
• Progressing though the story opens up the other sections. Once unlocked, you can travel between them all via horse, walking, stagecoach, or train.
• You can use lassos and kerosene lamps
• Marston is the only person you play as
• Deadeye is still in and includes two skill levels
• Duels are still in
• You can carry up to 4 items
• You can't own property
• All items will be shown on his model
• Regenerative Health
• You can do deadeye and fighting while on a horse
• Full day and night cycles, ped system similar to GTAIV and dynamic weather system
• Dynamic roaming wildlife such as wolves hunting for rabbits or mountain lions looking for someone to feast on
• No load times transitioning from world to interior
• The game will include multiplayer
• Mid-mission checkpoints

Personally, the more I hear about the game, the more I cannot wait to get my hands on it!

Source: IGN