Ending ruined entire series for me. Massive plotholes. No closure. Generic Dues Ex Machina ending.
The game is great up until the end. If you have multiple Sheperds from Mass Effect 2 I suggest stopping the game after the Reaper Destroyer on Earth is defeated and imaging your ending and then starting another character.
The co-op multiplayer is fun, its fast and exciting and you can increase the diffculty settings to make it more challenging. Even on the lowest setting it can be challenging because its a team game and some people are very bad at it. I'd like to see a MMO with combat just like it.
I finished my game with 35 hours and all quests done, be sure to go to citadel often and to read your ingame emails they add much to the game.