Claudine Beaumont at the Telegraph found Halo 3 a thrilling experience:

Bungie has done an incredible job with the online elements of Halo 3, which allow you to participate in online co-operative battles across the Xbox Live arcade, or indulge in multiplayer operations where you can create your own battle maps. It’s a thrilling, visceral experience. One of the highlights is a fully dynamic in-game camera that will record the action as you play, allowing you to review it from literally any angle in the game and make screengrabs of your best kills or near misses.

Beaumont finished Normal in six hours, which she calls a "single sitting" for a hardcore gamer. If you're really that hardcore, though, you should be playing at Heroic, like Bungie keeps saying.