The biggest problem a lot of people are making right now is setting everything to max and expecting their $$$ video card to handle it. Simply put, I don't think there's much out there that can handle "full boat" settings just yet... at least not for most of us.
Even with a great video card you may have to do the following:
-Disable shadows on other planes
-Turn shadows down to 4096
-Turn AA (Anti-Aliasing) down a notch or two from max