Yeah, that was fun. I enjoyed it right up to the final stage, which was a bit too repetitive (do more-or-less the same thing n times), and the time limit destroyed the casual pacing of the rest of the game (stop and read the graffiti!). The puzzles were generally easier than I expected, and I only got really stuck a couple of times.
Technologically I found the Steam client and Portal itself to be overly crashy on the new MacBook Pro, with the graphics subsystem often seizing up when I tried to exit or switch out of the game. This might be due to immature graphics drivers, or their inability to shuffle state transparently between the two cards. It also required a hack to get around its case-insensitive filesystem requirement.
Valve looks like they've overcooked Portal 2, with many more ways of getting around. We'll see in a few years time. :-)