I know this will have been done to death, but its a great game, and the story is brilliant, up until the end. IMO the ending is completely pointless, yes you find everything out about your choices, but to leave the option of you being perfectly able to carry on exploring but then still just having a anding where nothing else can be done is just stupid in all honesty. At least when fallout 3 did it they showed you, you couldn't carry on.
Of course this is just my opinion so take it with a grain of salt, but my personal thoughts is that they easily could've let the player carry on playing afterwards.