The best Fallout 3 DLC to date
Point Lookout adds more of everything you (probably) love about Fallout 3 to Fallout 3. To start with, it takes place in an entirely new area, not unlike The Pitt, but unlike The Pitt, there is a lot to find and explore for diligent players. Besides the main quest line, which in itself is fairly meaty and should take you 2 or 3 hours, there are interesting side quests to uncover and plenty of locations containing new enemies and loot.
The town of Point Lookout is surrounded by a swamp, whose aboriginals are none too thrilled about visitors. The town itself is almost entirely deserted. On the outskirts you will find shacks with natives, old mansions that look like they date back to the 19th century and festering marshlands. The main quest does a good job of making sure you see a lot of it, and there's an achievement for those who explore every location. I highly recommend this because you'll see some weird and wonderful things that you'll easily miss otherwise. Like in Fallout 3, not everything is signposted and you'll have run-ins with some interesting characters. One of the sidequests is particularly long and compelling, even including a trip back to the Capital Wasteland.
At the end of the main quest, you get some nice rewards, including a science fiction-esque gun that zaps people and leaves nothing but dust, not unlike the plasma rifles. You might be interested to know that the rewards are the same regardless of what choice you make towards the end, just like in The Pitt. The moral quandary isn't quite as interesting but you'll have to make a somewhat interesting choice regardless. It's worth noting that Point Lookout is also the most difficult content to date and you'll probably want to be at least level 20 before braving the bayou.
Overall, Point Lookout is very easily worth the 10 dollars, as it adds a hefty chunk of new content. You'll be hard-pressed finding DLC for any other game that offers quite as much value. There's a large new area to explore, and not unimportantly it is actually fun to explore, and the main quests, as well as the side quests, are pretty entertaining and as good as most quests in the main game.