Yes, of course, Fox News is biased. And so is CNN, MSNBC, et al. And it's simple, too. All sources of news are biased because people are biased.
And I think it's unfair to compare Fox News to, say, ABC News since ABC News doesn't run a 24-hour channel. The more appropriate comparison would be the non-opinion/commentary broadcasts at Fox News and ABC News broadcasts.
Many of the people here are unfairly lumping in O'Reilly and others as though Fox News presents them as news broadcasts when that certainly is not the case.
Also, I think many people see a major bias at Fox News not because Fox News is intentionally being a conservative broadcaster. Rather, it's because Fox News presents news in a more centered, straight-forward manner than it appears right-wing when viewed against CNN, MSNBC, et al which, imo, are hardly presenting the news in any neutral respect.