First off, go check some of the Ending Credits song lyrics: a post I made!

Will make my post short and simple:

The best: Completely new game-****genre/feel for video games. The portals idea is genius.

The good: The game has a very nice gameplay mechanic. The sound is very good. The graphics are clean and good looking.

The story, even thou it's very short, opens a lot of possibilities for future sequels/prequels, that, as stated on 1005s blog, connect with Black Mesa and the Half Life series directly.

The not too good (there's nothing bad in this game): Incredibly short. Maybe some future releases of more puzzles, and user created challenges will add a lot to this game. Lets just wait!