I got used to scrolling windows with the TrackPoint. So I wanted to get this functionality back. The trick is to put the following two lines in your /etc/X11/xorg.conf:

Section "InputDevice"
        Identifier  "DevInputMice"
        Driver      "mouse"
        Option      "Protocol" "IMPS/2"
        Option      "Device" "/dev/input/mice"
        Option      "ZAxisMapping" "4 5"
        Option      "Emulate3Buttons" "yes"
        Option      "EmulateWheel"
        Option      "EmulateWheelbutton" "2"
EndSection

You may not want to enable this if you rely on the middle mouse button for pasting copied content in Linux.