I may as well throw in my two cents.
I first saw Melty Blood at the anime club of my alma mater, Dawson College (before anyone asks: yes, that Dawson College). I was impressed at how deep and polished it was for an amateur fighting game. As I started getting into it, I became aware of its roots, an adult visual novel by the name of Tsukihime, and decided to import both Melty Blood and its expansion disc, Melty Blood -Re-ACT-.
Frequent message board visits fueled my knowledge of Tsukihime and Melty Blood's backstory (which struck me as incredibly well thought-out for what was supposedly an "anime porn game"). To date, Tsukihime is regarded as the best amateur game in existence, and puts many commercially available visual novels to shame (Do You Like Horny Bunnies, anyone?).
When I learned that Geneon Entertainment was making an anime adaption with great artwork and music, I was psyched. Upon viewing it to completion, I was... how to say... less than impressed. As I said, the art is nice, the music is wonderful, but the plot is half-hearted, at best. Excellent setup, lackluster development. To quote Keith from Six Feet Under: "You've just taken a small step forward, and now you wanna take a giant leap back?!?". Many of the subplots of the original game are hinted at, but none of them are explored. It's almost as if they were telling fans of the original "see, we didn't forget about this", only to cancel their actions in the following episode (ie: Satsuki's fate, Hisui & Kohaku's dark history). It's a pity, because it could have been great if they actually followed it through.
The art in the original Tsukihime isn't nearly as impressive as Melty Blood, but its story is superb. Imagine combining supernatural and mythological creatures (vampires, zombies) with modern day life without seeming ridiculous or contrived (on that note, I cannot call Tsukihime a "fantasy" title in the slightest). The title has been extremely successful, and has enabled its creators, Type-Moon, to go pro. Their first commercial venture, Fate / Stay Night, has been well-received and has managed to spawn PS2 ports, an anime adaption, and a sequel (Fate / Hollow Ataraxia). Tsukihime has also spawned a pretty good manga adaption, which has already been released in the US.
I am pleased that Mirror Moon has come this far with their translation projects. With a completed Tsukihime patch and the promise of Melty Blood and Fate patches on the horizon, I have plenty to look forward to in the not-too-distant future.
Funny, I always thought Wind -A Breath of Heart- was going to be released first. Oh well.