Since reading about Portal that was coming in my pre-order of Orange Box I've been waiting to see how they'd updated the game. I managed to play a 5 level demo at WCG since Valve had a stand there. It was pretty much what I expected, nice and slick though. Couldn't figure out how to put the box on the trigger the first time playing it, but others may have not solved it either as later on there was a big sign on the monitor saying "PRESS 'E' TO PICK UP THE BOX". The guy on the stand was from Valve too, so I had a great chat with him regarding Portal, TF2 and all things Steamy.
Finally got a chance to sit down and play it today, and although it only took ~2 hours to finish the game, the final level was AWESOME. So involving, it really felt like you're breaking out. The end credits were even more spectacular with a Johnathan Coulton song
Portal song on MySpace