defaults write com.apple.Terminal FocusFollowsMouse -string YES
Also with XQuartz, you can set X11 windows to focus follows mouse in the Preferences > Window screen.
In addition one thing I've always missed is being able to lower the Z-order of a window to the bottom of the window stack by clicking on the middle (or third) mouse button on the window title bar.
I do NOT care for copy-on-select, I like copy to be an explicit action. That way I can select, copy, select, paste to replace. With copy-on-select, you have to select, paste, select, delete which is less natural for me.
Just got my Mac. I am trying to figure out how to efficiently run a Linux virtual machine.
Edit: Figured it out, DNS issue: sudo apt-get remove libavahi-common3