Now as for other aspects such as art and story. I dont have Black Boobara so cant comment on voice or story. The art is amazing as far as the amount of tiny details go. Sprite is also fairly cute, reminds me of a bubble head thing you put into your car.
Now for the negatives of her design - I will not factor the boobs. She is after all Black Boobara, and there are some people who like that stuff.
She is fairly nice and thick but not fat so you have something to grab onto.
I am not a fan of that pale purple skin of hers though... what the heck, did she fall into a Galaxy ray disco chamber ? As far as we know I believe she is human, not some demi-human like elf chan, neko, inu or foxy chan, or as I recently learned an Oni like tiger lily, so that skin makes little sense, other than the artist own expression.
Consistency is the name of the game for her design, All 3 artworks are nice, though personally the Evo art is pure shit due to her expressien and the way she poses with her boobs. i do appreciate her Bloom art softening her facial features a tiny bit and showing her actually smiling. My favorite though is the basic first form. While I like my "sexi" as any other guy, I think the market is oversaturated with "too slutty". The basic artwork shows her clad In a yukata-ish attire and while shows some skin it keeps it all nicely packed for your imagination to explore. Classy is the word.
Compared to some 6* girls whose artwork is so simple, stale and just boring due to pale color palette and absolute lack of any details I think BB is definitely up there as far as quality and painting skill goes.
Voice, Scene & overall Vibe:
Now as I said, I have not seen her scene, nor heared her voice. However bunch of people call her sadist. Though some did say thats not entirely true and its more like she simply has a strong Ram like personality. Cant judge that honestly. Dont really like S&M shit myself so that would be a turn off for me.
Ultimate Design
As for the design of her Active skill - considering she belongs to the games Early characters where compared to some of the never girls those ultimates just look bland and boring (the devs sure did progress with their skill as far as making the effects more epic over time.), never the less I think it fits her theme, isnt completely unmemorable, and that slow motions backwards jump she does during it is pretty funny... you know Max Paine and all that old school hollywood stuff