The Geekend blog at TechRepublic was pretty taken with Halo 3:

Then, something happened that I did not expect. I got caught up in the storyline in a way that I hadn’t since Halo:CE. I didn’t even realize how immersed I was until I “came to” about four hours later with my stomach rumbling and a mild (lack of) caffeine headache because I hadn’t even stopped long enough to wet my whistle with my Live Wire. As I wolfed down the taco salad they catered in for us, I actually started to feel relief that I wouldn’t have to write an article panning one of my favorite games.

They don't give the game a score but do go to the trouble of listing vehicles and weapons.

Warning-- this review spoils the first cutscene!