Don't listen to these dumbshits. Halo 3 ODST is another achievement of the Halo universe.
Set to be a cheap expansion for Halo 3, the Bungie burst it's boundaries with so much content that Microsoft couldn't ship it as JUST an expansion.
Halo 3 ODST offers what Halo 3 didn't; Firefight mode (similar to Gears of War's Horde mode) and an slightly open-world campaign that brings a lot more fighting and action and slaughtering aliens. The gunplay is brought back its roots of Halo - health packs and no dual-wielding, which means every gun is useful on its own. You can also hold one extra grenade of each type (why didn't they have this is Halo 3?) bringing the total to 3 each, and also gives weapons kickback, making it a little more challenging to get kills. Brutes are actually tough this time around and knocking off their armor actually has a purpose.
As for the musical score, Martin O'Donnell
hits it right on the mark. More jazzy than Halo 3's techno, it sets the mood nicely. He proves once again that he can craft incredible music for videogames.
Even though the campaign is short and people may say it isn't worth the buy, ODST brings different experiences than what Master Chief could ever bring. It certainly is a step up from its predecessor, and any and every Halo fan and Xbox 360 owner MUST play it.