Disclaimer: Please read my Fallout 3 review first where I go into more detail, thank you.
The first DLC released for Fallout 3 was Operation Anchorage.
This DLC has you helping out some soldiers by entering and completing a simulation of "The Battle of Anchorage" before the bombs fell. Keep in mind that if you die in the simulation you die in the game for some good reason.
In terms of loot, you can get yourself some really sweet stuff such as the Chinese Stealth Armor which makes you invisible while crouching, Winterized T-51b Power Armor and the main attraction, the Guass Rifle which is like a Sniper Rifle that uses Microfusion Cells and is generally much more powerful.
My advice here would be to attempt this at a fairly low level ( level 8 at least ) so you can make good use of the spoils of war.
As to be expected, there are glitches such as game freezes and ( I'm not sure if it's just me ) random spontaneous combustion.
Overall, it's worth picking up for the weapons alone and you get a nice little story mission along with it.
Operation Anchorage gets 8/10 Chinese Stereotypes.