I didn't hate the ending. It wasn't bad, its just sort of a "the end of a long journey" type thing instead of some epic moment and a Cole Train rap, you know? The stuff leading up to the ending is pretty cool, though. There are also several choices to make right at the end. If you can see it coming, you can save and try out a couple variations.
Ok, so I'm going to make some spoilers here. The first is where NOT to go if you don't want to be put on the fast track to the end. [spoiler]Do not go into Vault 87.[/spoiler]
However, you can do stuff leading up to that point. [spoiler]Like the Little Lamplight stuff.[/spoiler] After that you can stop and go do other things.
Ok, some big ending spoilers here. Do not read unless you want to know the ending.
[spoiler]So the kidnapping of me was totally unexpected. I was able to convince the president to blow himself up, which was fucking AWESOME once you get outside. Choppers flying away, crashing, the entire base exploding. Cool stuff.
At this point I think you can still just wander off and not finish the game, I'm not entirely sure. I just didn't try. Though I think its better to stop before Vault 87 just for story consistency. "Hurry, you must help!" and then you wander off for weeks and everyone waits for you. Yeah, don't think so.
There was one thing about the ending I didn't like, though. Ok, this is super double secret spoiler. If you're reading this without beating the game this is your second warning. This next part is pretty much the very end of the game. Stop now.
Ok?
Good.
So at the end you have to start up Project Purity. You can decide to insert the FEV if you like. I didn't the first time, then went back to my save and did. It just changes part of the ending stuff. Well, all the choices do but it determines whether you get a good or bad ending.
Anyway, the part I didn't like was the choice of who has to start the thing. The control room is highly irradiated so whoever goes in there will die. Do you go in and die for your cause like your dad, or do you send in the girl you heartless bastard? The problem was I had a 3rd option, or so I thought. Fawkes, my best buddy super mutant that I saved from Vault 87 was with me. What did he do in Vault 87? He went into the highly irradiated area to get the GECK for me. So I was like "Dude, get in there and start the machine. We'll die, but you should be fine." and he tells me some shit about my "destiny" and that he wouldn't take that from me. It was kind of crappy that Bethesda thought enough to give him the line, but not enough to make an ending for the people that figured out he would live through it and everyone would be saved. I was like "Get in there you lumpy bitch, you owe me!"[/spoiler]
So yeah, good times. I don't know if I'm going to go back to an earlier save and continue doing all my sidequests or if I should make a new character. Or if I should take a break from FO3 and play something else and go back later. We shall see.