The best of the DLC by far
Broken Steel expands the plotline post-ending to open-end the game somewhat, taking in the obliteration of all the Enclave at the hands of the Brotherhood. Along the way, Prime gets surprised, you get to go UNDER Old Olney, and you gain possibly the most ridiculously overpowered gun ever - the Tesla Cannon...
This is the motherlode DLC; the level cap's raised to 30, a new post-ending plotline is added, there's a whole new set of perks, enemies, everything! It's pretty much everything you could want for a DLC, and then even more heaped on the top. It even has more gamerscore for the achievements than the others (150 rather than 100)! The extra plotline adds quite a good while of play, the new enemies add a level of challenge (they're all amazingly tough, and require some new strategies - I've seen YouTube footage of Deathclaws losing fights with the Albino Radscorpions, seen for myself as Fawkes got taken down by an Overlord with a bit of backup, and seen Reavers decimate whole camps of Raiders), the new Perks add some interesting possibilities (and make karma perks so much easier), it just has everything. Definately the must-buy of the bunch.
Achievements-wise, it's the same as ever; quest line for half of them, the other 3 Karma at level 30.
