The only Fallout 3 DLC worth buying, and I say that loosely.
Broken Steel picks up two weeks after the ending to Fallout 3, it turns out that the one way ticket into the Purifier at the end of the main quest wasn't so one way after all. You awaken in the Citadel with Elder Lyons hovering over you like a creepy pedophile. Good thing you're over eighteen, am I right? Anyway during the two weeks that you were in a coma the Brotherhood of Steel continued their fight against the Enclave, and Broken Steel is about finishing that fight.
At times Broken Steel's main quest feels more like Operation: Anchorage, than the Pitt unfortunately. You spend most of your time dungeon crawling and blasting away enemies than engaging in conversations and finding alternate ways of dealing with situations. Broken Steel does include a heck of a lot more content than the past two DLCs, though. Along with the main quest you've got a a few side quests related to the aftermath of Project Purity's activation, a few new encounters and changes to the game world that reflect the new events. You've also got a few new items including a new set of Enclave Power Armor. All in all I wouldn't say that Broken Steel's main quest is a better ending, but at least it has less plot holes since there's very little plot to begin with.
The big features that Fallout 3 fans were looking forward to are the raised level cap, and removal of a definite ending. Bethesda said that getting to level 30 would be difficult, yeah right I got from level 20 to 25 in only two hours and I did nothing but the Broken Steel main quest in that time. The removal of a definite end is nice I suppose, but like Fallout 2 there's little point in going on as by the time you finish with Broken Steel you've probably already done everything there is to do in the gameworld outside of mods.
Broken Steel is definitely better than Operation: Anchorage and The Pitt. It has more actual content, it makes a few drastic changes to the game, and it's less buggy. Unfortunately Broken Steel's main quest feels like a tacked on action game much like Operation: Anchorage, and the real enjoyment comes out of seeing what has happened in the two weeks since Project Purity was activated. Regardless, even if you're like me and didn't think that Anchorage and The Pitt were all that great, Broken Steel is probably worth giving a shot.
+ Fixes the plot hole filled ending of Fallout 3.
+ Raises level cap, if you care about that crap.
+ Some of the new equipment is nice.
+ The Puppies! perk makes Dogmeat not so useless.
+ Less buggy than the last two DLC packs.
- Main quest feels more like an action game not unlike Operation: Anchorage than an actual role playing experience like The Pitt.
- Not enough new content in the Wasteland not concerning fresh water and the Enclave.