Didn't you listen to the little robots ? They are hilarious !
Didn't you look around ? When going 'behind the scenes' (like in the walls and stuff, and the last level) it was so cool. The contrast between the white levels and the rusty metal stuff in the walls, and the "the cake is a lie, the cake is a lie" stuff on the wall was ingenious !
Also the big robot was so funny, trying the reversed psychology xD
Even though it still was more like a demo, it's still awesome !
I believe Portal was just a project game, it was never intended as a full game. But it's popularity has paved the way for the forthcoming Portal 2, a fully polished game.