It's a really good series! It keeps you hooked with some obvious trucks, though - episodes always end with cliffhangers, there are numerous "timebomb" characters scattered throghout the series ready to burst into action, there is fanservice (minimal, but if you see how many doujins this has sparked ...) and new characters are always introduced, forcing you to keep up to date with all the intermingling plots.

But I'm not complaining about the complex plot - that's how good anime stand out from bad ones!