For those that care, it is a very ecchi Harem series and your standard "Fighting makes girls lose all their clothes" anime. I generally like fighting anime and feel an amused indifference to ecchi, but if you really liked any of the following anime, you'll probably really like High School DxD:
Ikkitousen, Freezing, Ichiban Ushiro no Daimaou, Queen's Blade, or Sekirei
The plot of the story is basically Demons vs Demons (DxD) in a highschool setting, set in a world where there is a stalemated war between Demons, Angels and Fallen Angels. There are a lot of chess references as well, enough in fact that they become integral to the plot as lesser demons (Pieces) are enslaved to their master (King).
The art is very good and the series has one of the more interesting ending credits you'll ever see. Characters are stereotypical Moe, but in no way are any of them badly done.
Overall, is a decent anime. If you love Nudity and Girls Fighting anime, this is a must watch. If that type of anime offends you, skip it. Otherwise, it is a decent anime that you may not watch over and over, but at least you won't regret seeing it.
Note: Some versions may be heavily censored.
