In the package of the Orange Box it's great but it wouldn't stand out on it's own....
Don't get me wrong this game has great points like the great graphics and the fantastic sounds. The game has alot of humour in it too but it doesn't really come out till the final level which is a shame. Just what Portal lacks is length and a proper story and level structure because atm it feels too much like a series of small levels until you hit the final one and it opens up. That really sums up the whole game for me, how the last level is really the only good one. I really love all the atmosphere it creates and the computer womans voice that talks to you throughout and has some great sarcasm too but it's just a shame it's sooo short and never picks up till the last level. What i also found weird was how it's dead easy until like around level 11ish and then it suddenly just becomes harder so it has alot of pacing issues.
The sound of the game is fantastic with a great script and music. The credit song at the end is very funny and really really good actually. The graphics are all top notch aswel and even though the source engine was due to be released in 2003 (not released till 2004) it's still looking fantastic and one of the best looking games out there. They really manage to create a experimental atmosphere and really sciencey lol.
So theres not much more to say other than it's a funny game and worth playing as you get it with the orange box. However it's too short and the game doesn't really get good until the last level, maybe these portals however might work their way into HL3 or even episode 3.