When I saw the first episode I thought this was going to be such a great show. Full of mystery and all kinds of sci-fi goodness. Sure it had a naked girl right at the beginning so I guess that should have tipped me off some, but I figured it was just Gainax peppering the anime with some good old fashioned fan service.
But then came the second episode and the fan service turned into all-out moe -- just a romance with a some unrealistically "ideal" girl who is focused on the show's hero. And that just continued for half of the show. Where's the monster attack that we saw in the first episode? Where's the transforming Takeru?
Needless to say I was totally disappointed with those episodes. There was lots of nudity, but for a variety of reasons (the vague age of the girls not being the least) it was more awkward than titillating.
The second half made up for it some by bringing dark-Hikari out and developing the sci-fi part of the show. But the characters still felt shallow and I at the end I don't think it really saved it from the boring first half. Too bad. Maybe if those fan-service-oriented episodes were combined into just one or two episodes it would have been better.
The animation was average. Cool monster designs, but that was about the extent of it.
The music was nothing special. I liked the opening song, which was sung by the same person who did the opening to Evangelion. And I liked the closing song in the last episode, but everything else was average.
Overall, the show promised a lot of action and sci-fi intrigue but put off delivering on it until the second half of the series. I understand that the director was intentionally trying to break expectations and create a kind of dichotomy in the storyline, but unfortunately he didn't do a good job of it. That, combined with the shallow underdeveloped characters made for an interesting but overall disappointing show.