Playing to your weaknesses
Fallout 3, the base game, has a lot going for it. A huge open world to explore, a ton of character customization options, competent conversation and morality systems, the list goes on. Fallout 3 was great because it could be approached in a variety of ways, each just as valid as the next. For the first Fallout 3 DLC, Operation Anchorage, this all has been thrown out the window in favor of an extremely linear, extremely combat-oriented romp through Alaska.
Not real Alaska of course- from D.C. to Anchorage is quite a long walk- just a simulated version of the frigid north. The DLC is focused around a military simulator used to recreate the liberation of Anchorage, Alaska from Chinese Communists, an event referenced throughout the game. As opposed to the drab brown of the Capital Wasteland, Alaska is much more unique in appearance, covered in blueish ice and snow, providing a much better looking area to play around in.
You'll get a few new toys to help you make your way through the Alaskan campaign, such as an energy-based sniper, the Gauss Rifle, and some new melee weapons. All of these can be brought back into the Capital Wasteland, which is nice, but they still don't help to make the combat any more compelling. If you're only in it for the gear however, the Alaskan campaign is very short, a few hours at most, meaning it won't be long until you can get back to shooting Super Mutants with your shiny new equipment.
Anchorage performs one specific task, and that task is combat. If you did not enjoy the combat in the base game, you will not enjoy Anchorage. If you enjoyed the base game for reasons besides combat, you will not enjoy Anchorage. Anchorage is a combat pack, and as such will not be enjoyable to anyone besides hardcore Fallout 3 players and combat enthusiasts. Even then, at ten dollars, the short campaign and meager gear rewards may not be enough to make Operation Anchorage worthwhile.