For those of you who haven't been keeping up, this isn't a sequel to Portal. In fact, it's really just the original game with a handful of new challenge maps included. Many of those new maps appeared for free on the PC, though, so if you've been keeping up over there, all you really have to look forward to here is a set of new achievements.
The company's marketing blog also posted this audio file in order to get you stupid pumped for Portal.
Maybe it's too early (you know, noonish) for me to wrap my mind around this, but wouldn't a clip of GLaDOS beckoning you to return to the world of Portal only make sense if this was an actual sequel and not a barely upgraded re-release of the original game?
Oh well. It's probably been close to a year since I last played Portal. I'd play it again. But then, I already own it on both the 360 and the PC. Hmm... is there really anyone out there who hasn't played Portal who would be better off getting this instead of just going whole-hog and buying a copy of The Orange Box instead?