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.
Comments
Count me in on missing focus follows mouse too. FWIW, you can get Terminal to support this by:
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.