Buy this game.
Allow me to explain why every gamer should buy this game:
1. It's beautiful. The art and music in Braid is some of the best I've seen in a while. The watercolor graphics and folksy tunes allow the world to really suck you in.
2. It's beautiful! The gameplay and puzzles give surprisingly depth to what first seems like a derivative platformer (look for several Mario nods, especially in the first level). The different ways in which time can be manipulated in each level offers fresh challenges every step of the way. I encourage left-brained players to experience these puzzles side-by-side with a right-brained friend, and vice versa. Both will find the game intriguing and challenging, and you may need the help!
3. IT'S BEAUTIFUL! The story is extremely well crafted, and it's worth a few plays (or at least reads). The ambiguous, mysterious nature of the plot is very fresh for game writing. The ending is definitely a "BWAH?!" moment.
4. We need more games like this. This is a platformer. Metacritic shows that it is the 10th rated Xbox 360 game. Imagine what games could be created if this type of originality were applied to different genres. We need to pay Jonathan Blow $15 each, not necessarily so that HE may go on to make amazing games such as these, but in support of the idea that ALL game makers put this amount of care and craftsmanship into their creations.
So do it. Now.