As noted on GLaDOS@Home, the release of Portal 2 took place in the wee hours of this morning, just after midnight eastern time. The preorder bonus for the puzzle sequel is gone, but you can get 10% off on a two-pack, and 60% off on the Potato Sack + Portal 2 bundle.
Up to chapter 6, my only minor whinge is I do not find that the voice of "Whelly" (the blue sphare thing) fits - it's to human, I would have like to have it with a little fx on it.