Kasumis 1 Hour Memory.
The DLC starts out with you recruiting Kasumi Goto from the Citadel, and after a short intro, you go off to, some planet i forgot the name of, that looks kinda like earth, then Shepard gets his sexy on (Well, a fancy suit.. thing) and you have to infiltrate a party of some big-wig criminal under the name Solomon Gun, it starts out with you casing the joint and looking for ways to get into his room to get his DNA to get into his safe so Kasumi can uh, get, some thingy i forgot, again.
But, this cool sneaky spy Shepard gameplay doesn't last long, and you once again get back into the rooms full of enemies and conveniently placed cover, and after 3-4 playthrough's of this, you kinda wish you could have been sneaky again, because its a fun diversion.
The loyalty mission is one of the best in the game, Behind Thanes and Samara's, and Kasumi is an interesting new character
The DLC all in all is short, pretty fun, especially if you enjoyed Mass Effect 2 as much as did, but, as its fairly short and nothing spectacular, its not quite up to scratch for priced DLC.
However, if you need more Mass Effect 2 like a jiggy 48 year old heroin addict needs another score, then don't miss this.
Oh, and the scenery looks awesome in HD.
[Edit: Oh, right, the DLC is almost twice as long if you play on insanity, the boss battle is a bastard]