Different optical technologies
The "optical pots" you're talking about are most likely a simple encoder wheel, somewhat similar to the encoder wheel on a mechanical mouse. (We use a lot of their precision cousins -- as relative rotary encoders on servo motors).
The Sun optical mice you're talking about were, IIRC, made by Mouse Systems, and had to be used with a special pad with lines, since they had an optical detector that counted the lines. In essence, similar to a relative linear optical encoder (e.g. as used by many DRO's (digital read outs) on knee-type vertical mills).
The Agilent optical mouse (MS started off using HP/Agilent, but then switched to their own design IIRC. Logitech still uses Agilent, although the their second generation design), OTOH, is more like a small camera, looking at the 'texture' of the surface and trying to track bits of texture. That's why they won't work on surfaces with no texture.
So you have to give the PC world (via HP/Agilent) credit for optical mice that work on most surfaces, no special mouse pad required.
Tony
