After watching the first volume, I was immediately hooked. El Hazard is upbeat, hilarious, and very entertaining. The mood is generally light, but things get more emotional in the later epsiodes. Amusing, well-developed characters coupled with an interesting plot liven up the whole series. There are several subplots, but all are smoothly interwined with the main storyline.
Characterization is very distinct even for the minor cast members.
Witty dialogues also contribute a lot to EH's overall appeal and humor. The art and animation are excellent throughout. It's actually better than the original Japanese version, which is a rare case. This is one of my all-time favorite OAVs. El Hazard has spawned a TV series, and two more OAV series.