Shadows Over Camelot is currently one of our favorite board games. It has a bunch of good things going for it.
1) It's a cooperative game - For some reason, I really like cooperative games. When I play games, I play with people that I like, so it's fun to be on the same team with them. I think the same thing goes for sports or video games. I'd usually rather play with one of my friends than against them. I know not everyone feels this way, but I do. There aren't a whole lot of cooperative games out there, so it's nice to have one that's well made.
2) You get to be either King Arthur or one of the other knights of the Round Table - I've always liked the King Arthur stories ever since I was a boy, so this is a great theme for me. The only problems that I could see would be if the people you're playing with start humming the songs from Excaliber throughout the game (which has happened) or make dumb Monty Python jokes the whole time (which has not yet happened). The knights all have different special abilities which adds a bit of flavor to each game.
3) It's a Days of Wonder game - As with all of the Days of Wonder games that I've seen, the components in this game are very nice. The artwork on the board and cards are fantastic. There are cool little miniature catapults and invaders. These could have easily have been cardboard tiles and not have affected game play at all, but having them as miniatures just makes the game seem that much nicer. And there's always the benefit of the Days of Wonder customer support should you ever need it.
4) There's a TRAITOR! - This is a cooperative game, but there is always the possibility that one of the players is a traitor. You have to make decisions as a team, but there's always the thought in the back of your head that one of the other players is trying to thwart your efforts. Before the game, each player is dealt one of eight loyalty cards. One of the cards says 'Traitor' on it. So the traitor is not necessarily in each game, but the possibility is always there.
Now, we haven't actually played with a the loyalty cards yet, but we have a good reason. And that reason is...
5) The game is hard! - When we played the first time, we got clobbered. The 2nd time we tried, we came close. On our third try, we barely won. In order to win, 2 of our 3 players had to sacrifice their own lives for the good of the team (one of these players was Mrs. BigKat. She really didn't want to do this. I mean she REALLY didn't want to. When I suggested it, it was clear that she didn't like the words that were coming out of my mouth.). And keep in mind, that we did this without playing with the possibility of a traitor! It's nice that the game is difficult because it really gave us a sense of accomplishment when we won.
Anyhow, if those reasons sound appealing to you, then I would highly recommend this game. So far, we've only played 3 player games (the minimum), and it sounds like it is even more fun with additional players. I've read that some people say that they have gotten to the point where the game has become too easy. But on the Days of Wonder forums, there are suggestions for making it a little harder. For us, that's a ways off. I think the game is plenty hard as it is.
You can get this game at places like Boards and Bits for ~$34. A little on the expensive side for games, but well worth it, I think.
Want more information? Try checking out Board Game Geek. They've got a lot more info and reviews over there.