Mass Effect 2 won a member's choice vote to discount most of its add-on DLC this week by 50% - for XBox Live Gold members only. However, even if you are a card carrying member, this apparently doesn't mean that you can get all of the DLC at a discount. Glaring omissions include the Overlord DLC, Genesis, and all the item and alternate appearance packs. On the upside, Arrival, Lair of the Shadow Broker and Kasumi - Stolen Memory are sporting a tempting discount.
400 MS points
Liara T'Soni is tracking down the mysterious Shadow Broker, and no one is safe. She'll do anything to recover the man the Broker kidnapped… and the Shadow Broker's agents will do anything to stop her. Team up with Liara and chase clues from the luxurious heights of Illium to the Shadow Broker's own secret lair. Adds the Shadow Broker intel center, new research, and five new achievements – and the chance to continue a relationship with Liara.
Widely considered one of the best DLC BioWare has released to date, Lair of the Shadow Broken partners you up with one of your potential love interests from the original Mass Effect in a substantial side mission.
280 MS points
Cerberus has procured the service of Kasumi Goto, the galaxy’s most enigmatic master thief. In return for her help, Kasumi has asked Shepard's help on a dangerous heist to infiltrate the vault of a deadly master criminal named Donovan Hock. Gain Kasumi’s loyalty on the planet Bekenstein, where Hock is throwing a party for the galaxy’s richest and most deranged criminal minds to recover data of great importance to Kasumi... and to the galaxy at large. Adds a new squad member, weapon, research, and achievement.
The "other" DLC that gives you a new Infiltrator squad mate, Kasumi Goto, and accompanying loyalty mission. Unfortunately, Kasumi's place in Mass Effect 2 isn't fleshed out that well, but she is a robust henchmen nonetheless.
280 MS points
A deep cover operative has gone missing in Batarian space, days after reporting conclusive evidence of an imminent Reaper invasion. Shepard must travel to the edge of the galaxy, rescue the Alliance agent, and discover the truth behind the Arrival. Uncover new research and three new achievements in this spectacular new mission for Mass Effect 2!
This is the final piece of Mass Effect 2 DLC to be released. It was considered pricey for a short (1-2 hrs) mission that bridges the story of Mass Effect 2 with the upcoming Mass Effect 3, but for half the regular price, it might be worth it to you for the story. Unusually enough, Arrival has Shepard winging it solo, so you may miss the squad dynamic that you are used to.