I find complaints about the left wing bias trite due to the accusation being bandied about by the likes of NP every time Bush makes a rightfully criticized mistake. It's like the story of the boy who cried wolf, except this boy and his legions of mindless lackeys all have megaphones.
Karl Rove is the man who got and kept Bush in office using machiavellian tactics; he's the Republicans' freaking MVP! Hiring him as a political analyst is about as unbiased as hiring...well, who's the closest thing the democrats have...Bill Clinton?
Other news stations have their biases, but they lack that extra bit of hypocrisy that comes from claiming to be neutral at least once per commercial break.