Graphics par excellence. Sound quality, excellent. Plot, great. Puzzles, excellent.
This game is excellent. Graphics, sounds qualtity, voice actors, plot.. there is rarely a grey area. The only complaint is that it is somewhat short - even coming into the game dry (with no idea how to play it) it shouldn't take more than 8 hours max to finish.
Otherwise, it is an excellent game, which all FPS fans and puzzle afficionados should acquaint themselves.
The puzzles start off simply, though some of them require more timing than planning, by and large it is a 'this goes here and then that goes there' style of puzzle. With the added complication that if you line it up wrong, the stuff you're trying to redirect can kill you.
The creators of the game deserve a salute. Portal is engaging, interesting, and bizarre in a glorious fashion. They also achieved what Prey didn't. Made the game fun.
Oh, and the song at the end was great :)