I prefer a dark mood in a game like this. Like someone else said before, the Galaxy is pretty much under control of the Sith, a cheery "theme" really wouldn't fit in with what's going on.
I liked playing with Jedi and blaster using party members, having vibro-using characters in your party is pointless, I'd rather use Jedi with lightsabers.
Well it was never confirmed that the Sith actually wanted to kill you. In the trailer with Sion narrarating it's clear that the Sith intend on converting you to the Dark Side rather than killing you.
Not sure yet. That dude with the silver plated suit keeps being labled as "Mandalore," even on the official site, but I'm pretty sure Mandalore is already dead, so how is that possible? Unless it's just an error and really just another Mandalorian.