I've been having a ton of fun with this game. Between my girlfriend and I's two characters, we've put 173 hours into the game already - and there's still so much I haven't done yet.
Settlements are awesome, I'm currently setting up my home base on Spectacle Island. Gigantic area, and the idea of having an island fortress seems fun.
Settlements are pretty cool but I wish they would get raided by bands of raiders or super mutants. I spent all this time building up a huge defense to never getting attacked once. I'm sure a mod will come out and make it a much better experience, the benefits of PC.
Mine have been attacked a few times. It's not often, and they never attack with more than four or five people it seems like. So far only Raiders have directly attacked my settlements, but I do see marauding bands of Super Mutants around. When you kill them, they have a note with orders saying to raid.
The settlements have repeating quests as well - help, so and so was kidnapped, can you clear this Super Mutant/Raider camp, etc.
I look forward to mods adding stronger raids, and maybe some more variety. I'd like to see packs of deathclaws, or a Behemoth attacking my settlement.
I also look forward to mods that improve the general clunkyness of settlement building.