I finally beat the game last night, and I have to say, it's one of the best I've ever played, and I don't usually like FPS. It just has an epic feel to it. Some might be disappointed that it's not the epic Earth saving battle Bungie hinted at with the E3 demo, but it is still an epic battle. The graphics are gorgeous, the sound effect are some of the best I've ever heard, the game constantly moves forward (as opposed to Metroid Prime, which moves back and forth over places you've already been to), the levels are huge, and I can't wait to play through it again.
That said, it is still only a game. Don't expect it to get you laid, or to raise your children, or to become your salvation.