Mass Effect 2 (2010) is considered by many as the apex of the Commander Shepard trilogy of video games. However, like the first and third Mass Effect games, it was expanded with more adventures, squad-mates and devices.
The Cerberus Network Pack contained squad-mate Zaeed (Robin Sachs), his loyalty mission, the Firewalker missions and the Normandy SR-1 Crash Site.
Kasumi: Stealing Memory contained squad-mate Kasumi Goto and her loyalty mission.
Overlord (my personal favorite) shows a Virtual Intelligence with autism, who had sensory overload.
Lair of the Shadow Broker expands upon a sub-plot in a vast scale that made it feel like it should have been in the game.
Arrival serves as either the great foreshadow for Mass Effect 3 (2012) or the great prologue to Mass Effect 3, depending if you completed the original Mass Effect 2 game.
All of the DLC except Cerberus Network and Arrival are integrated into the PlayStation version of the game while the other versions of the game have the expansions to buy (not just Cerberus and Arrival).
For the non-PlayStation players, the total of the extended edition content price is $30.96 excluding tax.
All of the content especially Lair of the Shadow Broker can have a lasting impact for those who are ready to begin Mass Effect 3.