Braid is now, and has been for a day or so, available for PC users. You can get it from Greenhouse, Steam, Gamersgate, and Impulse. The reason I post, rather than to simply let you know it’s out, is because Jon Blow, the game’s creator, has been posting troubleshooting tips on his blog.
If you have a problem running the game, take a look and see if your problem has been solved there. Blow suggests to new customers that they should try the demo first, to see if it will run on your computer. I’ve had no problems with the game so far, and I’m enjoying it a lot. Some of the puzzles are fantastically designed, so well done to Jon Blow on all fronts today! Braid most certainly gets my seal of approval, and I strongly suggest that you at least try the demo.