Halo 3: ODST | 10

Concept: 7/10
Halo 3: ODST introduces a new Special Forces Recon Soldier for the Halo Universe. The Orbital Drop Shock Trooper is a darker, ligher armored version of a Spartan with silent weapons. That's pretty much it.

Story: 9/10
The story is very well written, well told, and well acted by Firefly and BSG veterans. It is really entertaining and one of the best parts of the game. However, it is told through flashbacks and is somewhat difficult to understand your first time through. You might be confused at times, but in the end, it all makes sense.

Gameplay: 8/10
It's Halo 3, with a couple new guns and a slight improvement to the health system. Your character sounds 'in pain' when your health is low, reminding you to stay behind cover. There's also a night vision visor that you can toggle on and off. Unfortunately, the game seems too dark if you don't have your night vision on, and if you use it in areas that are fairly well lit, you're almost blinded. In the end, the night vision seems extraneous. The game would have been better if the dark areas were just a bit brighter, but still cloaked in shadows.

Level Designs: 6/10
There is an open ended city area where you can explore and Convenant troops are being dropped in to battle. This is new to the Halo Universe and it works quite well. Most of the game takes place in New Mobasa, a futuristic African City that is being invaded by the Covenant. The look and feel of the city is pretty impressive, but overall, the levels feel redundant. Fight in corridors, defend an area... You know you've got problems when the Campaign is only 5 hours long, and the Missions feel repetitive.

Sound: 9/10
The music is foreboding and adds to the grim atmosphere while the effects bring the battles to life.

Replay Value: 7/10
You can start the campaign after lunch and finish it before dinner.
There is a Firefight Mode which is like Gears of War 2's Horde Mode, but ODST features an additional challenge where each wave of enemies has a special behavior like "Dodges Grenades." This mode is for friends and invites only. I understand that Bungie is trying to prevent the Leroy Jenkins of the world from ruining the fun, but it really sucks to not be able to play a pickup game.
There are 3 new Multiplayer Maps for Halo 3, too.

Maturity - The game is rated M because the Halo series is rated M, even though the action is pretty tame.

Overall: 7/10
Buy this game if you're a Halo Collector, you've got a bunch of buddies that still play Halo 3 and will use the Maps and Firefight Mode.
Rent this game if you just want to play the Campaign. It's only 5-6 hours long.

I'd recommend waiting for the price to drop before buying ODST because if you spend $60, you're going to feel ripped off.
$35 for this game feels about right.