First of all - I must admit I was looking forwards to Red Dead Redemption. I'm not a huge Grand Theft Auto/Sandbox game fan, but Rockstar has a record of doing it well. I'm particularly fond of Bully (Or Canis Canem Edit if you're in the UK.) and Grand Theft Auto 3: San Andreas.
The things that make these games enjoyable to play are the sense of freedom and the strong narrative. What you can find though, is that these aspects of gameplay are not always comfortable bedfellows.
When Red Dead starts, it introduces you to the game world with a long cut sqequence, which tries to set the scene, tell you a little bit about the world John Marston lives in. Then it morphs into a very linear, super basic tutorial - which acts as something of a prologue to the main story.
Gameplay wise the first thing that grabs you, is the first time John Marston mounts a horse and you try to control it. The horse riding is excellent in Red Dead and is almost enjoyable in it's own right. it's certainly enjoyable to watch and to ride fast accurately takes a different skill to previous games where your man would be driving a car. The controls are fairly intuitive, particularly if you are used to Rockstar games, and the additional features in Red Dead make sense and only enhance the experience.
Story wise, it reminds you of classic westerns, like Clint Eastwoods 'Spaghetti Western Trilogy' and 'Once upon a time in the west.' It's probably a grittier western than the likes of 'The Magnificent Seven' series, but better for it.
The story also constantly reminds you of the agenda or point, the characters are constantly debating and philosophizing about change and whether it's good or bad. This can give you a false impression that there's a deep meaning to the story. Which personally I don't think there is.
Once the game proper starts, your man is based in and around a small town called Armadillo - his mission to take out a man called Bill Williamson. The Sherriff offers to help for a few favours off John, but you get to a point where you really feel the frustration of the main character, because you start to feel that this is largely a plot device intended to drag the story out. There are little tutorials spread out through the first act and you meet some interesting characters, but it does seem like a particularly long-winded part of the game.
Once Williamsons Fort has been invaded the story only seems to improve, and gameplay elements are spoon-fed to you throughout the game, keeping it interesting.
All the gameplay elements work well, some better than others, but nothing really strikes you as 'off'. The world of John Marston is a very free world, you can take on all manner of jobs and tasks and to complete 100% of the game would take significantly longer than to complete the main storyline only. The problem with this, is that once you've finished the main story it's hard to motivate yourself to continue playing...
I found this with 'The Saboteur' too...
It's still a great game though - to get the most of it, play through the extra content at the same time as the main story - otherwise it will end up on the shelf largely unfinished.