The DLC for Mass Effect was disappointing, but Bioware are looking to rectify this in the sequel where DLC will be available from launch and more is scheduled to arrive. When buying the game you will get a code that unlocks the Cerberus Network, and allows you to access the DLC.
"The Cerberus Network augments and extends the rich universe of Mass Effect 2," said Dr. Ray Muzyka, co-founder, BioWare and Group General Manager of the RPG/MMO Group of EA. "We're thrilled to be able to reward loyal BioWare and Mass Effect fans with ongoing, high quality content and provide a direct channel for our players to dive deeper into the intriguing lore of Mass Effect."
Here are some further details on what to expect:
"Players who access ‘The Cerberus Network' will receive the first DLC pack on January 26th (launch day in North America) featuring new missions and in-game items. Included in this pack is a mission that introduces Zaeed, a rugged and deadly gun-for-hire who is recruited to join Commander Shepard's mission to save mankind.
After launch, BioWare will release another DLC pack for Mass Effect 2 that introduces the Hammerhead, a new vehicle in the Mass Effect universe. This agile hover tank features improved handling on rough terrain and maneuvers deftly in combat -- a necessity for players travelling across harsh planetary environments throughout the galaxy. In addition to this new vehicle, BioWare will release new missions and unique in-game items, including Cerberus Assault Armor which boost shields, health and heavy weapon ammo and the M-22 Eviscerator Shotgun."