This is a paragon example of a great concept with amazing execution. It may seem like a generic ecchi anime on the surface, but it quickly evolves into a deep and thrilling story-driven work of art.
Story:10 The story itself is one of the best of all time, it manages to use elements from both Catholic and Demonic mythologies to create an action-packed fight for power. But action isn't all this anime has to offer, the story focuses more-so on the characters' own development as individuals and how the different characters try to initiate and prevent the overtaking of hell. It's about a fallen angel strategically plotting her next move to go against the odds and find the place where she truly belongs.
Art:10 The art is appropriately vibrant. The setting and characters both have near-top-tier design which are suiting to their respective roles/personalities. Their proportions and detailing are both great. You can really feel the chillyness of frost areas, and the oompf of magic attacks. To generalize, almost everything is above average, it's major eye-candy.
However, there is a problem which affects most anime- The airing version has a couple bad frames that look out of place. These are usually fixed when the BD comes out though. *The censored version's censorship is somewhat abundant too.
Sound:10 The girls' voices come across as being clear and they all sound like they fit their respective bodies. The SFX all pop up at the right times and there aren't really any times where it feels like they've missed a sound opportunity. I'm being a bit humble in saying that there wasn't anything wrong with the sound; rather, it is perfect.
Character:10 Each of the main and sub characters have aesthetically appealing designs as well as really nicely fleshed-out archetype personalities. How characters react to each of the twists and turns is somewhat predictable because of this though. The creators did a stellar job of implementing personalities based around the Seven Deadly Sins without making the characters too overboard or eccentric. Their attitudes make it that much easier to get involved with the serious feeling of the story.
Their costumes are all on the skimpy side, but they still manage to reflect and reinforce the characters' personalities.
Enjoyment:10 This has been an absolute rollercoaster of fun so far, and it looks like things are just getting started! The story and characters are amazing. The art and sound are absolutely delicious. It's hard to find anything about this anime which can't be enjoyed.
Overall:10 This anime is above par in all of it's aspects. It wouldn't be an overstatement to say it is an absolute masterpiece that's easily one of the top 10 anime to have ever aired.
Even if someone dislikes a certain aspect of this show whether it be demons/angels, fight scenes, ecchi, ect...- There are still tons of other high-quality features which can be enjoyed.