If you like stories centering around ancient mysteries and trying to break from your past, then the Sith Inquisitor story is for you. Just be aware that the voice acting is NOT mostly sinister or authoritarian at first, in particular with the male voice actor, there's a greater focus on snarky humor and...upper class lines, I suppose I would call it.
Personally I think the female voice actor, Xanthe Elbrick managed to nail the tone I wanted for my Sith - someone who's been kicked around most of her life, but is now given the chance to rise above it, so she grabs it; quite ruthlessly I might add, though she never succumbs to pointless cruelty for the sake of pointless cruelty.
So think about what kind of character you want to play and go from there. If you're more into being the underdog who rises through the ranks and ends up a master manipulator, then definitely give the Sith Inquisitor a try. If you want to be a generic "******/evil" type character, then you should try a different class.
Edit: Oh and yes, your greatest enemy with the Inquisitor will be BioWare's binary morality meter. Pretty much any quest that doesn't have a specific Inquisitor angle to it, is written as either Evil Sadist/Cuddly Puppylover in terms of DS/LS choices. Hoping we get more...subtle DS options in the future.