It's a great price, but the main reason I'm posting here is because I'm almost certain someone (Mercutio?) liked the original MS Intellimouse. It's available via a clearance special right now at Mwave.
Actually P5-133XL, I bought my first optical mouse in 1990. It was made by Mouse Systems, in Fremont, CA.
The thing about optical mice back then though was that they required special reflective mouse pads. Do you remember them? They were mirrored surfaces, covered with light blue and light gray intersecting lines. Crossing those lines was how the mouse detected it was moving. I think it's the same idea as how my Logitech trackball works (it has a red ball with black dots patterned over the surface). Anyway, those Mouse Systems mice with their cool mouse pads were also available for Sun Microsystems hardware. I remember thinking I'd scored a pretty neat product, because my mouse was the only PC version I ever came across -- all the other identical mice I saw were for Sun SparcStations, etc.
Anyway, to answer your question Paugie, no, the Microsoft Intellimouse is not optical (well, not outwardly). It's a regular mechanical design with a rolling ball. Internally it uses IR sensors to watch a pair of X-Y wheels spin, but that's nothing special. I think all mechanical mice use that trick to figure out where the mouse ball is rolling.