I have seen it several times on some news reports that those who get most of their news from Fox actually know less real news than those who don't use that as their main source, and this was supposedly confirmed in three separate studies. However, I never actually checked those studies out, so I'm not presenting the above as some sort of slam-dunk fact. Maybe someone here has?
Whether it's true or not, the one thing that I find totally bogus about Fox is that they interweave opinion in with their news coverage. To me, if it's news commentary, such as what Fox has in their evening time slots, that's fine and dandy, but it shouldn't be in their basic news earlier in the day.
I think a great example of how far Fox is off-base occurred with their coverage of the last election whereas they were literally shocked when Obama won, even though there was some rather clear-cut indications that this would likely be the case. They say Hannity's audience dropped by roughly half because he was so insistent that Romney was going to win hands down. The morning after the election, I watched about a half-hour of the morning show on Fox, and their depression was like they had just lost all of their best friends.
If Fox is supposedly such a good news source, how could they have been so off on their predictions? I would suggest that it's probably "confirmation bias", namely that they believe in their own opinions to the point of delusion.