Unknown numbers, no. My policy is: "If they really love me, they'll leave a message." (Then I'll pick up while they're still talking).
We have caller ID that shows on the corner of our TV screen. I love it!! I don't even have to go to the phone to decide not to answer it (which is great if you have a cat on your lap!) I've even taken to playing the "music choice" channels instead of the radio when I'm not watching TV, just so the caller ID is on.