As a promo, this is pretty nice.
I'm actually still playing through Ys IV, so I cannot comment on the story much. it looks like they got the same folks to do this as they did with Ys 2, and it looks outstanding. I love the way the characters look as well as the animation. Sad they did not make this into an anime, but it's a cool video nonetheless. This video is available on Youtube, so take a look at it when you can. It's only 3 minutes.
Oh and the music? Easy 10. The Ys IV soundtrack always bangs.
Short review:
This show is just OK. I've never played Xenosaga, and came at this with a fresh set of eyes. I found this show a bit slow and boring at parts. Sometimes the audio is mixed strangely so you can't hear what the characters are saying.
I still had fun though, but not THAT much fun. I finished the show an hour ago and it left no impact on me aside from the last 3 episodes, which even those, though way better than the other parts of the show, where still pretty OK.
The show is OK. Fans will probably like it.