The story isn't too horrible, but rather generic. Disaster in Japan/only one guy (with hidden powers) can save the world with lots of action type. The animation and sound are above average. Interesting characters, they aren't always very original either though. Some fanservice here and there -- well, the girls are pretty.
In a nutshell: nothing groundbreaking, but worth watching once. The mood changes around halfway. Most people seem to like the second half, I do not -- it becomes pretty chaotic here and there, with too many random things popping up. Also, I found the ending rather disappointing. And by that I mean crap.
With a decent ending I would have given around 8/10 overall.