I've read this complaint on AVS forums and this is why no one updates firmware unless there is no choice.
Samsung does not offer a way to go back so you have to make it a warranty issue and insist "yes it is" in spite of them calling it "working to manufactured specs."
Nod to AVS Forums.
I have samsung led tv UE40B8000. Picture was good. Then I updated firmware to last one ( T-CHU7DEUC-3002.1 date 21.04.2010). Also I changed some settings from secret menu because i wanted to turn off local dimming. Now picture is realy ugly, dark, i cant watch my sd channels because it is too dark and colours are strange, blacks are too black (even in dymamic mod with backlight 10). Please help me and tell me what i can do to return back good picture. If someone have default service menu values it will be helpful. Thank you