just got valkenhayn (sp?), makoto, and mu. my opinions:
Valkenhayn R. Hellsing - his name annoys me a little ('hellsing' works for 'alucard'), but that small gripe aside, he's a freaking beast--pardon the pun. Haseo's great with him, but could use more practice. His drive turns him into a wolf that can dash in any direction (like Bang's Fu-Rin-Ka-Zan), taking chunks of his drive gauge in doing so.
Makoto Nanaya - reminds me of Dudley from SSF4, only as squirrel girl on crack (most of the time). she's an absolute blast to play. Her drive is punching things, you can charge her drive attacks for more range and damage if your timing's right, and her 214 A, B, or C launch you at different heights toward the opponent so you can mix up your combos to a hilarious degree.
also, her astral finish punches you THROUGH THE MOON.
Mu-12 - we've only played as her a little, but she's been giving off this 'broken to all hell' vibe, since shes's Lambda with LASERS, LASERS EVERYWHERE. also, online i found out the hard way that mu has an infinite juggle, and that the state of the BB non-ranked community has decreased sorely for the nighttime hours--nothing but spammers and cheesy exploits everywhere. it makes me sad.
all in all, they're really fun.