Playing through it again to get the stars (you have to delete you save game to do this), I just think this game is actually pretty bad the second time around. First time you play it, it is great because you have to figure out all the puzzle and shit like that, but unlike Portal which holds up through repeated playings, this game doesn't let you figure out ways to solve puzzles quicker or anything. It is basically retracing your steps and doing tedious actions to solve the puzzles you already knew. I mean, when you don't have that sensation of 'oooh! I feel good after solving that puzzle' or some shit like that, you see the game for what it really is: dealing with terrible platforming mechanics as you follow a script. You have no freedom during your play through of this game and are forced to do exactly what Blow wants you to do. The only leeway you have is the platforming, which is incredibly clunky and at times feels broken to restrict you from doing a puzzle any other way than what Blow wants you to do.
Bottom line is that if this wasn't an XBLA game and on DVD or CD, I would suggest returning it after one playthrough. Great once and bad a second time. Only reason to play it a second time is if you have amnesia and don't remember anything about the game.
In fact, I will go as far as to say that Braid is probably going to end up being the worst major XBLA release this month. Geometry Wars 2 is better, Bionic Commando Rearmed is definitely going to be better, Galaga Legions is probably going to be better, And Castle Crashers is also most likely to be better. I'm not saying it is a bad game (at least for the first playthrough), but the amount of hyperbole surrounding this game is misguided.
If you can find a way to play this once, I would say it is totally worth it, but now that I realize how little replay value this game truly has, I would say that it isn't worth the cost. I'm just glad I got it for free.