One of the most common complaints about the first Mass Effect was the dearth of DLC following the promise of a bounty. Mass Effect 2 has been almost opposite. While the DLC hasn't had a massive effect on the gameplay yet, there's been plenty of it. Better yet, almost all of it has been free to those who logged into the Ceberus Network when they picked up their new copies of the game.
The bonuses had to end somewhere, though, and the Kasumi Stolen Memory pack marks the first paid DLC for Mass Effect 2 (not counting the horse armor, I mean character costumes). Like the first downloadable character, Zaeed, Kasumi is a mysterious, shadowy character that joins your mission on the condition that you help her with her own quest.