These days I use a ThinkPad X41 Tablet primarily and I have not been using a mouse for years. So it was a pleasant surprise when I used Ipe on a desktop one day and notice that the scroll wheel on the mouse actually does something quite useful: it zooms the canvas.
Now the TrackPoint system on ThinkPads actually supports scrolling as well, but it does not work by default in many applications because of some technical issues that you don’t want to know. In any case, to configure your ThinkPad so that its middle scroll button works, insert this line to your Windows\System32\tp4table.dat and then reboot.
*,*,ipe.exe,*,*,*,WheelStd,0,9
Update: Actually all Qt applications don’t have scrolling in my ThinkPad. To add scrolling to all Qt Widgets, add this line instead:
*,*,*,*,*,QWidget,WheelStd,0,9