When I first finished the game, I was utterly disappointed. I just sat and stared at the screen for a good fifteen minutes in disbelief. It wasn't only the quality of the writing or anything like that, but what hit me the hardest was the abruptness of the ending and how shocked I was at what you DIDN'T get than by what you did get. (i.e. you dont get to learn about the effects all your actions have after the game ends)
However, after reading online and checking out forums, I realize that I was completely wrong about the ending. The problem was that BioWare walked one of the most delicate lines of all when they picked the ending. It HAD to be the way it is, otherwise it would have been a disappointing and obvious ending with no one even wanting to play the last half of the game. Instead, they made you think, made you work, made you fight.
By now, the majority of the outrage expressed by gamers is in relation to the fact that there is absolutely no closure. We spent three games making choices, sacrificing, and fighting to save the galaxy, but in the end we don't get to see what effect our choices had. That's why their pissed. It felt like, after putting in the work, BioWare laughed in our faces and said "It didn't matter."
But i'm getting off topic, so I'll wrap up: The ending itself? I like it. The fact that you don't get to know what happens after? HATED IT.
Still, the game was epic, and one of my favorite games of all time.