Actually, I find when it comes to just straight news reporting, Fox is fairly down the middle. I'm talking NEWS here, like what you see and the top and bottom of the hour, or what you hear on Fox News Radio updates, so the slogan works on that aspect.
However, all of the commentators and many of the anchors/hosts on Fox (big difference) certainly come off as conservative. And that's where the line gets fuzzy for some people, since a lot of stuff on Fox News isn't, well, news. Dayside, O'Reilly, Hannity, Colmes are all commentaries of the news.
(That said, I really like Shepard Smith. But he's not for everyone. He's one of those guys you either want to punch in the face or buy him a beer. But he did say blowjob on the air once during a J-Lo story, so he gets much love from me.)
But remember the cardinal rule here: if you agree with it, it's not biased!