I take this opportunity to advocate that you go read the manga before you try this OVA. The manga is light years beyond this drek in terms of... well, pretty much everything.
Needless to say this OVA does NOT do the manga any justice. Some of the animation sequences are pretty, but beyond that, this just sucks. The characters come off flat and obnoxious, and the story seems pointless and haphazard--there is no tension, and it feels like there are no stakes. This does not feel like a semi-Apocalyptic war between the forces of Heaven and Hell. It feels like... well... like every other bad pseudo-Biblical post-Evangelion catasterfuck of an anime.
If you're hardcore Christian and would be offended by a rebellion against God being told from the perspective of Fallen Angels, skip it. If not, skip it anyway and read the manga. You'll be glad you did.