Great game, despite its very brief single-player campaign.
Still, the amazingly immersive storyline that had me almost drying my eyes at the campaign's grand finale, superior production values, the addition of a nice easter egg level/mini-mission after the credits roll, a number of cool achievement ideas, and a very enjoyable multi-player component that adds a nice RPG-light touch to the experience makes this game one of the best shooters on the Xbox 360.
If you don't like multi-player, however, I would recommend you rent it, as it's just too short for a $60 single player title.