ODST is an impeccable game.  The story is awesome, with real, gritty, regular characters fighting for a real goal.  Nathan Fillion, Alan Tudyk and Adam Baldwin make every bit of dialogue an exciting addition, especially with IWBYD on, the added Firefly references are just incredible.  Though it isn't worth the price of admission the campaign is a sequel in every right and kicks the ass of every Halo game since Combat Evolved.  The multiplayer is just about everything we've ever wanted out of a Halo bot-fest.  It's bleedin' challenging, intense, and piling up heaps of dead uglies around your feet is so gorram'd satisfying I thought I might just asplode with delight.  Though the ommitance of MM is a shame, working with your friends to survive is much more fun than playing with random (uncooperative) strangers a la Horde Mode.

Throwing Halo 3 :Mythic in is basically doing this; we get Halo 3 with a different campaign (ODST), new multiplayer mode (Firefight.) and thirty dollars worth of maps for the same fragtasticness we've had a might longer than two years.

ODST is worth every penny when you put it into perspective.