I'm not noticing people reacting to me any differently, whether I'm good or bad karma. There doesn't seem to be any particular motive to stay on the good... or evil... path. And don't mention to me the "Lawbringer"/"Contract Killer" perks. Any speech options or...any reactions to me?
Companions, certain Karma options in diolouge, On the GNR raido bad karma gets you talked down on, normal just explains what you did, good karma, people look up to you like a god. It also effects the walk by talk of people. Like you walkpast someone and they say "Hey!" and that stuff.
http://www.youtube.com/watch?v=zcZ3wXF3r14 There's a douchebag hiding in the rocks with a radioactive twinkie! - LRN2BFBC2
Asides form the above, there's also how having your Karma at Very Evil or Very Good gives you access to daily freebies. Very Evil intimidates the slavers of Paradise Falls into giving you things, Very Good persuades the random settlers in Megaton to repay you for...whatever.
You can mess with the karma system. I'm precluded from using certain followers, but I can do what I want, and I got the Regulator perk so that I can get payment for fingers of evil characters I have to kill anyway. Plus, the Regulator packs stopped showing up to smoke me. The BoS still greets me and lets me walk among them. Perks also exist to reset karma so you can get the most powerful follower in the game, and this follower won't leave even if you misbehave once again.
Being good takes a lot of discipline because it's just too much fun to test new weapons on lightly armed nobodies.
The Talon Company bozos come after you regardless.
The only places you'll see serious dialogue change is in Paradise Falls and Megaton. This was sort of mentioned but not the extent to which it is. If you're Evil before going to Paradise Falls you can get in without having to do the quest beforehand and everyone treats you like you're great stuff, I think you also get new even "better" speechs when you go Very Evil. Vice-versa for Megaton being on the good path.
Who lives down in deepest darkest Africa? Kimba the White Lion is his name!
Um, you don't need a certain Karma to get lawbringer/contract killer, you have access to both at a certain level..and i think you could take both, but contract is pretty useless as the only friendly people you come in contact with who actually want to kill you are very few and far between....maybe like 1/20 for good/evil. Unless of course you just go on a killing spree in megaton...but thats not evil, that psychotic.
Also, Karma lets you do certain things, evil or very evil lets you get in paradise falls for free, no entry fee or quest necessary(i think its very evil.) People don't say stuff about you when you walk by with good karma, it determines what squad attacks you out in the wastes(talon or regulators), it determines what kind of "ending" you get after activating the purifier/how your father reacts to what you have done, but most importantly it determines what followers you can get. As an overall concept, it is pretty much represented in every single quest you do, you can be good or evil.