The Trailer is beautifully made and has great music! it rendered beautiful classical style scoring which I like in the PV. The anime is adapted from Reki Kawahara's light novel "Sword Art Online", the anime will debut July this year with a planned video game too. The story is very similar to Hunter X Hunter's Greed Island arc because it follows the same policy. You can't leave the game until you cleared it, though in Hunter X Hunter you need to learn Nen as a requirement. But in the anime, you just need to enter in the game through virtual reality so the moment you die in the game is the moment you die in real world too.
Stay tune for updates of the anime when we hear news from the community. Will iron out my blog so I can put up some subscription links in my future posts.