Just finished the game yesterday. I tried to get a happy ending for all the factions I cared about.
I just finished tonight. Great ending, great game. It's like 1 million times better than FO3. I'm exaggerating a little bit. but it's far superior. Fallout 3 I quickly got bored doing side quests, and just wanted to get the game "over with". Not so in this game, I completed nearly every sidequest I could find with the exception of Searchlight. I didn't want to mess around with the radiation in that town. Radiation is annoying. Black Mountain was annoying too for that reason.
I'm not sure what I screwed up with Vault 19.
As for the followers, I'm not sure how to get a better ending for them. Maybe I missed a quest somewhere.
Who is Jason?
I only used a few followers during the game. I used Cass and finished her quest (violent way), used Boone and finished his quest. I was happy with both of their endings. The dog had a decent ending I guess (he has no quest I'm aware of). ED-E I fixed, but his quest was bugged. There's a bug in the PC version if you exhaust all the dialogue options with the lady at the scrapyard before you repair ED-E it bugs out.
Although I guess the game counted Lily as a follower, but I never really used her. The voice and appearance freaks me out.
Cass is by far the coolest follower. Boone was alright after you did his quest. But he didn't say much in casual comments. But that's part of his personality.
So one thing I wasn't sure of in this game was the order to do the ending. There were so many different ways it seemed to end it. I like that of course. Most games only have a "good" or a "bad" way, I like a game that gives a few more options. I really don't feel like replaying that much, however. I am starting a new game, but will wait until I finish more sidequests before I "commit" to my final path. That way I can see most possible endings. I am thinking of an evil-ish Unarmed/Explosives character. I figure I need explosives for things like Deathclaws. I'll probably use a lot of sneak too. I did in my first game until about halfway through. Then I was too powerful, and never bothered with sneaking as my Q-35 could wipe just about anything out. Except the tougher deathclaws. The legendary one was quite tough.
One question about the beginning. I think I found out midway through my game, but forgot.