Broken Steel is a satisfying conclusion to the Fallout 3 main quest, and a must have DLC.
There are plenty of new armour and weapons to be found. One set of armour you'll notice straight away if you're a higher level is the Enclave Hellfire Power Armour. It offers more protection than even the Tesla Armour, so watch out if the enemy is wearing it. An example of one of the new weapons is the Tri-Beam Laser Rifle, which as the name suggests, fires three laser beams at the same time. There's not only new weapons and armour, there's also new creatures, such as the Super Mutant Overlord and Feral Ghoul Reaver, both of which are extremely tough to kill and are very powerful. The Enclave also have Hellfire Troopers, which wear the armour I mentioned before and carry a Heavy Incinerator, which is a flame based mortar weapon.
Of course there's plenty more content to be found in this add on, but I don't want to spoil it all for you. Broken Steel is pretty much bug free, I haven't noticed any myself. It's clear Bethesda wanted to perfect this add on, and I don't blame them, it is the conclusion to the Fallout 3 main quest after all. There's just one little off putter. Where's my Lyon's Pride Power Armour? I'm sure I got recruited into that squad, but I got the normal Power Armour instead of the Lyon's Pride Armour. And new companions would've also been nice, such as Sentinel Lyons when you complete the main quest, but I'm just nit picking there.
In short, Broken Steel is well worth the 800 Microsoft Points, and it lets you tie up a load of loose ends in the Capital Wasteland.