If you've been in the general vicinity of me in the last six months, you have likely heard me raving about my new Thinkpad (I got an X61s last September). It's powerful, durable (I've dropped it on the ice once already), well supported by free software, and has great battery life. It's light enough that I don't think twice about taking it with me everywhere. But the thing that has impressed me the most has been the TrackPoint (the pointing device with many other names.)
I was somewhat apprehensive about buying a laptop without a touchpad, but after getting used to the TrackPoint I can't imagine going back. Touchpads are crude and error-prone input devices. They are easily confused if you let an extra finger or the side of your hand stray onto the surface. You have to constantly re-place your fingers to move or scroll long distances. Touchpads get grimy and crumby and acquire little dead zones. And, of course, touchpads are typically located many centimeters away from where you want your fingers to be while typing. So you have to move your wrists to switch between pointing and typing. It's practically uncivilized.
The TrackPoint is right in the middle of the keyboard, so you only have to move your index finger over the width of one key in order to use it. You can use it for both pointing and scrolling (just hold down the middle button and point; this works out of the box on Windows, and you can easily configure it under Linux as well). Just by pushing and holding in one direction you can move or scroll arbitrary distances. And the finger displacement needed to use the TrackPoint is on the order of millimeters, not centimeters.
The TrackPoint is a solid-state device which senses pointing via resistive strain gauges, and I have not had any reliability problems with it. Lenovo has developed some pretty sophisticated software which continually recalibrates the device so it doesn't drift.
When I heard that the scroll ball on Apple's Mighty Mouse (which is supposed to permit scrolling along two axes) acquires dust and grime really easily, I wondered if there was some more reliable two-axis pointing device you could put on top of a mouse.
Putting an optical sensor on top of the mouse might work, but I suspect that there wouldn't be enough feedback to make it feel natural, and you would also have to have a pretty fine optical sensor to figure out when your finger was (or was not) in contact with the thing.
But what about putting a TrackPoint on top? Is there a firm, I wondered, that was crazy enough to put a pointing stick on top of a mouse? As it turns out, Lenovo itself makes such a thing; it's called the ScrollPoint mouse.
From a quick Google search, you can apparently get one of these for around $25.