I've been watching this series on Netflix Instant and I'm pleasantly surprised! I haven't seen an X-Men cartoon this good since the original 90s cartoon! If it had lasted longer, I might even say it was better. It had a bit of a darker feel to it, I love the characters on the team, the animation is smooth and great looking, and the stories feel very comic book-ish rather than your normal "bad guy of the week" kids cartoon.
The storyline follows Wolverine gathering a the remaining X-Men together after a mysterious attack on the X-Mansion and Professor Xavier himself. The MRD (mutant-police) hunt mutants everywhere, and Wolverine decides he and his team must do something about it. Professor Xavier is in a coma, but awakes 20 years later and uses Cerebro to contact Wolverine and his team of X-Men in the past to try and prevent the dystopian future Xavier awakes to, complete with mutant concentration camps and Sentinels scouring the countryside for mutants.
VERY highly recommended. If you are a Marvel or X-Men fan, you NEED to check this one out before Netflix takes it off of Instant Watch and on to DVD again.