Fallout 3 - Broken Steel Reviews @ VideoGamer, Ars Technica

While we wait for Bethsoft and Microsoft to fix the PC version of Broken Steel, here are two very positive reviews. The first is from VideoGamer, who score 9/10:

The environments aren't fundamentally different to what you've seen before (although the Air Force base has trees!), but working your way through the new quest line feels like a cross between traditional Fallout 3 questing and combat-heavy scenarios reminiscent of Operation Anchorage. Now before you reach for your pitchfork, don't worry, the combat isn't shackled as it was in Operation Anchorage. Much of it takes place in buildings and environments within the map. Some areas are new, some are reused, and there's a dash of off-map travelling, but the point to make is that the combat is, unmistakeably, much better. Because the level cap has been raised and because you're up against tougher enemies, it feels more like the game did when you took your first tentative steps into a Metro tunnel, or explored an abandoned building for the first time.
…and Ars Technica says it's "worth your money":

Ultimately, though, Broken Steel is the extra content that fans of Fallout 3 have been waiting for. It provides an epic conclusion to an epic story and lets players continue adventuring afterwards, should they desire to keep on exploring and wrap up some loose ends. Not only that, but it makes the game challenging again, something that seemed to be missing for those of us who had maxed-out our characters and were traveling around with heavy-duty equipment.

Since this DLC affects the ending, expect spoilers. Still no obvious word on the status of Broken Steel for the PC.
More information.

IGN has one too… 8.5.

Makes it challenging again? Now that has my interest. Two-shotting the final boss was a horrible let down in the original game.