Originally posted by Depression
People who say the game is too short didn't take in the full experience. Have you heard all of Wheatley's lines? GLaDOS's? There's almost always a half-dozen or more lines that the AIs will spout if you ignore them, and to cut them off is almost a travesty. How about speedruns or least-portal challenges (granted they're not that easy on consoles, but with portal funneling and Valve giving really generous portal bumpers, it's not impossible)? There are about 3 or 4 ways to solves every chamber too, using techniques like portal boosting and peek-a-portal.
And if you're looking for a challenge, that's coming as free DLC (well, not sure if it's going to be free for XBox, but it definitely will for PC and PS3) plus if you have the PC version there are tons of custom maps already made and even more coming in constantly.