Does anyone know if additional content is unlocked if you beat the advanced levels and/or the least number of steps/portals/time objectives?

I loved when I went 'behind cameras', seeing all the offices, labs, etc. Pure amazingness.

After the test chambers, Portal changes from 'tech demo' to 'game' for me. Absolutely great in every way, from atmosphere to gameplay elements, to story developement.
Too bad the game's so short, I really, REALLY enjoyed it :(

Also, GLaD0S is a great character and has some of the best character developement in just about 5 hours time I've ever seen.
The boss battle is done really good, and proves combat with only the Portal gun is possible.

I love to see Portal's sequel to be a full game, instead of a 5-hour quasi tech demo.

At the end of the level with the companion cube, after you burn it. The game says something like " Congrats you have killed your companion cube faster then any other test subject" just the way it was said i started to laugh.

Plus the other parts with the talking gun turrets, omg put me down, where did you go, it was priceless.

At the end what GLaDOS started getting mad and insulting me while I tried to solve the final puzzle. Was hilarious hearing the things she said while desperately trying not to die. After playing through it I found a script online just so I could read any part I missed. First game I've ever done that for.

GladOS was easily the highlight of Portal, her quotes are pure gold.

"Remember when the platform was sliding into the firepit and I said 'Goodbye', and you were all like 'NO WAY!' and we pretended we were going to kill you. That was great. Someday we will look back at this and laugh. And laugh. And laugh."

As for the end battle, if you took your time with that and went at it slowly, she would taunt you with some of the best lines I've ever heard.

"It's all on file here, you're unlikable, liked by no one, extremely hard to like. Also, you are adopted. Haha."

:D

All the game is great, I got sad when I had to destroy the cube companion :(

What i also like about GlaDOS: We provide usefull information in training rooms that are life threatening. For instance: stay on this lift to clear the room, also if you fall in the water you die, your welcome :P

Warning this video contains CAKE spoilers, and Portal Song:

Enjoy

Portal for me was best game of 2007 hands down, and most innovative.

It was just perfection, from the slow release of the story and the oh so blackly funny dialogue to the best credits ever for any game.

GlaDOS was also the best character in a game for a long, long time even is she was clearly inspired by Shodan in System Shock (still one of the best game villans ever).

I really, really hope they take this gameplay and experience and expand on it without cocking it up.

Best bit for me was the first hidden room you uncover... pure genius and subtle as well.