I don't know if the developer has modified this since it was released, but I thought it was uniformly brilliant. I've got two recommendations re Braid.
My first is that anyones that downloads this does not resort to a guide as every puzzle has a deceptively simple answer, and contrary to the Zero Punctuation article I didn't find any of the levels or puzzles had arbitrary solutions. I was banging my head against a wall re one puzzle piece for about 30 minutes, but I just completed the game a few moments ago without a guide, and I don't think I would have felt satisfied if I'd headed over to Gamefaqs!
My second recommendation is that everyone downloads it
. The score, graphics, concept and implementation are all superb.