Whoa, this series is totally unexpected. I was thinking it would turn out to be some typical anime based of on a game following the usual story and such of the game but instead there's a big serious plot right from the start on the very first episode. Thanks to this plot, this anime might be really good.
So we basically get to see world where players that use these "head gears" that allows them to enter the virtual world which is of course, Sword Art Online. Their minds control their Avatars pretty much which is quite similar to Accel World anime and probably the Summer Wars movie. The first episode only introduced some of the basics of the world and setting but there is no more details until the second episode gets released. Overall, this anime series looks very good and I also definitely can't wait for the next one.
Conclusion: Sweet unexpected anime and I also can't for the next episode.
Personal Note: Oh, did I mention that there's a good OP at the credits? Don't miss it!