You're not alone. A moment ago I beat it for the first time too.
Absolutely everything was magnificent. Everything was leaps and bounds ahead of Portal 1 for my money. Brevity is nice and all, but when you have the dearth of potential that Portal brought on in terms of gameplay and characters, I can't help but want to see more, and it was The Dark Knight to Portal 1's Batman Begins in that regard.
It was just the right length for this kind of game, paced in just the right way, with the perfect amount of environmental variety...It was deviously challenging in just the right amount for my not-so-puzzle-oriented mind...
But the story and the way it told it...a psycho-scientific love story that was at once creepy, hilarious, sad, adorable, loaded with all sorts of unpretentiously presented subtext, and just incredibly fun, populated with some of the best developed characters I've ever seen in any medium.
I want a console Portal compilation that I can own separate from The Orange Box. Those games deserve their own disc release. In my Top 5 favorite games for sure. Up there with Metal Gear Solid in the "Can only be done in video game form" category, and that's the highest praise I can pay any videogame.