I think the problem with FOX is that it generally leans to right and when it does, it's often quite blatent about it.
From what i've seen, every news station in the world has its left-leaners and right-leaners and it very much depends on what you're watching as to what slant you'll receive. But I think it has to be admitted that usually FOX is on the whole biased to the right, while others such as MSNBC/CNN lean a bit to the left.
I find it odd in America that, generally, everything is so stuck to each of the two parties. In most countries I find that media shifts alignment from election to election (especially BBC which supports Labour when Labour's in power and Conservatives when Conservatives are in power - because it's the government in power which decide upon their funding!) whereas in the media I think it's almost always divided down the same line, unless you get two centre-ground politicians.
That's just a subjective view, though, as is any idea of 'bias' or 'unbalance' because in reality everything is biased to some extent in a direction.
But whenever I watch FOX I get a feeling that Republicans are great, warm, friendly people, and whenever I watch CNN I get the feeling that Obama is the messiah and I must vote for him because he'll change the world and make a difference!
A slight tongue in cheek moment (for those that don't pick up on those things) but hopefully highlights my point, it's also interesting as to what stories each channel runs. Often the idea of bias diminishes in a documentary covering both candidates because it's quite hard to intentionally spin the story either way, since that would be very obvious. But you could easily edit a couple of stories out - or in. I noticed that some news channels ran the Palin 'scandals' a good couple of days before FOX did, and even then FOX reported it as idiot bloggers, while others debated whether they were true and what this meant for voters (well, clearly nothing).