Ending is shoddy writing at all. Those who think it's full of plot holes or bad writing are taking the ending at face value. If you take the ending at face value, you are doing Bioware and the team that made this game a great disservice.
This ending is one of those endings that makes you think and requires you to use your imagination to fill in the blanks. Not your typical hero (LOTR) ending you were expecting, where Shepard destroys the Reapers, and rides off into the sunset with his love interest. Followed by a cutscene of showing how everyone in the galaxy ends up. Nope, they gave you an ending that made you think and use your imagination. They were never really going to explain the ending in full detail, because that would ruin their little social experiment. Not your typical gamer ending which is usually empty action or spoon fed explanations. This kind of stuff you sort of see in movies, but this is also a work of science fiction. Many gamers couldn't handle any unanswered questions or unexplained events (ending not making sense to them). They want it all spelled out for them.
http://social.bioware.com/forum/1/topic/355/index/10034971/1
^ Read that.
