Excellent Promise, But Lacks Length
One of the best things about Portal is that it does make a huge emphasis on the physics rather than combat itself, despite elements of 'lite combat' being present through the use of turrets. This allows more of a way to take a look at things objectively and try to make an educated guess with the physics as opposed to taking the game by pure force.
While the main character you play is silent, you do have two other "people" that prove to be very interesting. GLaDOS, the AI supporting your testing, and the little turrets that prove to be very interesting. While not wanting to spoil too much, these turrets do give you a sense of a conflicting feelings towards them between harmless and deadly.
The only real problem with Portal is purely it's length. It only lasts about an hour and a half assuming you don't get stuck trying to deal with momentum. However that is offset slightly with goal-oriented puzzles and more advanced versions of the test chambers available once you complete the basic in the story. On top of that, you also have a commentary available from the developers and even the voice actor of GLaDOS which proves to give a very interesting insight to what these designers were thinking giving a better appreciation for what they had done. The achievement system Valve has been implementing makes a show here, giving marks for various accomplishments in-game, however the requirements to unlock them are viable, thus ruining the fun in finding them.
While short, and of course only part of the Orange Box, Portal is a very fun, funny, and physically (in-game sense) intense game. This is a game that has been celebrated, and it should continue to be celebrated as there are even hints of a Portal 2 in the commentary.