I've been thinking about rewatching this recently, it's been a long time. Since it's been so long, I can't really discuss the finer points of the show.

One of the things that allows the show to be as good as it was is that it's an anime original. I like to imagine that anime originals are basically a portfolio for the studio, so a new studio can say "hey, we're available to hire, here's what we can bring to your project". Studios aren't a huge profit maker in the first place, so it can be a risky gamble (Manglobe went down for bankruptcy shortly after their second original anime Samurai Flamenco (which I think shines brighter)). So, with it being a gamble, the studio has to put more effort and passion into the project. There's also the bar of manga to climb over; you don't want to embarass your business with a bad story. So I'd recommend checking out other anime originals sometime.