The STORY for Trinity Blood had such potential that it kills me it didn't live up to it. I think that the basis was interesting - test subjects, vampires that eat humans, vampires that eat other vampires, the Vatican, brothers fighting (Trigun, anyone?), etc. Sure, not everything has to be perfectly original, but I thought it was a strong enough plot. However, it was conveyed so poorly. First of all, I think there was a problem with the length. When there is an anime with that intricate of a plotline, that's when you start planning your 50+ animes (and they can be good, if properly planned). But all of the information in Trinity Blood felt forced to be included in it's 24 episode span. (On a side note, while the Biblical names were interesting - they made no sense and followed no Biblical telling other than Seth, Cain and Abel were the first children of Adam and Eve recorded. But Lillith is not even in Genesis).
One thing that bothered me about the ANIMATION was the fact that women looked completely like midgets and men looked like these huge, bulky, broad shouldered towers. It seemed so disproportionate. And the men had these tiny, little faces set on this enormously large frame. Other than the design of the men, however, I have no complaints with Trinity Blood's artwork and actually thought that the designs for Cain and Abel's true form was interesting.
I don't know why I did this to myself, but I watched Trinity Blood dubbed; therefore, the SOUND score has lowered immensely. Unless you're Crispin Freeman or Steve Blum (or even Johnny Young Bosch as long as it's Trigun ONLY), then I don't want to hear the English version. Oftentimes they end up translating things wrong anyway and can end up completely changing a plot of an anime (Mononoke-hime, for example) but I also just find the quality of voice actors to be lower than that of seiyuu's. That being said, I did like Troy Baker as Abel, but most of the other voices made me want to stick a pencil in my ear. As far as music goes, I was very unimpressed with the OP and Ending. I could tell that they were trying to stick with the theme of the anime, but it felt off and unenjoyable.
The CHARACTERS were basic, in my opinion. I found Abel to be interesting, but ever so cliched in the bad-boy-gone-good way. That bored me. Esther seemed like the typical female character who is shy and sweet but has a hard core (her character in the manga is SO much better). Ion was bratty. I did, however, like Leon; so there's a bit of salvation there for me. There is nothing wrong with recycling a certain type of character, but I think it just needs to be well done and I didn't feel much in the way of character development from this anime. I believe that's due to the OVERWHELMING amount of characters in this short anime - so they tried to focus on the plot. Honestly, they just didn't have enough episodes.
Overall, I would recommend people to watch it once and keep an open mind about it. It wasn't terrible and I'm not upset I watched it or think I wasted my life on it's 24 episodes; but it's something that feels like it needs to be re-done, keeping only a few of it's original anime elements. I believed if they tried to stay truer to the Visual Novels, it may have been more successful.