It's easy to spot that 11eyes is based on an adult game. The experienced anime viewer's eye can see it within a few seconds based on the length of the skirts (which lead to frequent panty shots), the character designs, and even the music. What isn't easy to spot is that 11eyes relies on its story, not the cuteness or sexiness of its characters, to carry it - and the story so far is pretty good.
The tone for 11eyes is set pretty early, when the main character Kakeru has a nightmare about his sister's suicide. The imagery is serious, dark, and quite visceral. There are deep and heavy undercurrents to the events of 11eyes, and when Kakeru and his useless-but-cute friend Yuka are sucked into the Red Night, the world of the series becomes just as freakish and nightmarish as that opening scene. It actually reminds me a lot of Persona 3, which is a compliment - the world of the Red Night is a bloody, dark mirror of the real world, and the monsters just enhance that feeling.
The action so far isn't that great, as this is mostly a table-setting episode, but the groundwork is laid for a lot of interesting stuff over the rest of this series. The music is pretty good as well, enhancing the mood without taking over in an episode long on exposition and the creation of mysteries.
Overall, I'm looking forward to the next episode, where the suspense and action promise to ramp way up. I'll keep watching and let you know how it is!