If you're familiar with major DLC in Fallout games, you'll recognize that Far Harbor takes place in an area outside of the main map. For this one, you need to get a boat to travel, which is given to you as you begin the quest. You may also recognize that the new quest comes up by listening to a radio broadcast, this one involves a case Nick Valentine is working on. So, bringing Nick along is a good idea. Nick is familiar with the people involved in the quest and as you progress you'll see that his presence is relevant.
I think of Far Harbor as “Fog Harbor” because the fog in the area is significant and pretty much everywhere. It attracts the island's creatures and is radioactive. Some of the human residents of the island have set up fog condensers, which remove the fog and provides protection for a small area.
While I haven't finished playing the DLC, I've noticed that there are a few factions on the island and I haven't reached a point yet where I absolutely must choose a side to ally with. This may be something that comes up later. I have helped out a few groups on the island already, providing me with plenty of quests. So far, it doesn't seem as though I've run into any quests that are never ending, similar to the ones given to you by Preston. Quite a few of the quests are optional and I've tried to complete them first.
I've been enjoying this DLC. There are new creatures, new characters, new items, and new places to explore. Many of the island's creatures seem to be tough. I found some of them interesting, such as the Glowing Wolf, Glowing Radstag, and Glowing Yao Guai. Normally Radstags don't attack, but the Glowing ones certainly do. Some of these creatures may not be limited to Far Harbor, but I don't recall every seeing them elsewhere. You may also run into the very rare Hermit Crab, such as I did.
There is some new clothing including Marine Armor. I've found some of the new clothing, but haven't really used any of it yet. I'm still wearing mostly Robot Armor, which I got from the Automatron DLC. There are also new recipes, which use some of the new items you'll find around the island. One of them requires Wolf meat and Lure Weed. Be careful harvesting Lure Weed because one of the new creatures, called an Angler, has an appendage that looks like Lure Weed and lies hiding under water waiting to ambush it's prey (which means you).
There are some new weapons as well, but again I haven't really played around with them much. I did try out the new Harpoon Gun, which is pretty strong, but takes a long time to reload. I've not only found the basic version of the gun, but also two significant variations of it.
So far, I find Far Harbor to be interesting and it seems similar to other major DLC released for other Bethesda games. So, if you like the game, check out Far Harbor. Just bring some Radaway and Rad-X with you, or anything else you may find to help protect you against the island's radioactive fog. You're especially going to need it when you come across the Children of Atom, who bask in the warm glow of Atom.
Lastly, be warned, the DLC does have some issues. I read somewhere about people experiencing problems which seemed to be related to rendering the fog. I haven't had too many issues with it, but I've certainly run across a few bugs. One time, instead of walking around with me, Nick was actually swimming in the air for a while. I also ran into an issue where the game quietly crashed to the desktop while I was going through one of the puzzle-like quests.
Speaking of the puzzle-like quest, which you may find yourself running into it, it's not really extremely complicated or frustrating. It reminded me a bit of Portal. I was happy to complete it without looking for help.