I've used optical mice and I've used ball mice, but now I ran into something called optomechanical mice which seems to be a cross between the two...but I haven't found much information about them.
Has anyone used these? Do they have the same problems that ordinary ball mice have? Do they get gummed up with lint, then slowly stops being an effective pointing tool? Do they require a mouse pad?

I have an optomechanical trackball mouse. It's pretty good, but you'll need to occasionally remove the ball and wipe out the lint from the optical sensors. Here's mine: http://www.practicalpc.co.uk/reviews...k_explorer.htm. It uses a USB port, but it comes with a USB-to-PS/2 adapter. Linux treats it like a normal mouse.

As far as I know, all ball mice are opto-mechanical. The "mechanical" part comes from the fact that mechanical rollers are used to translate the ball's 2 dimensional motion into 1 dimensional motion of two discs. Each disc has a bunch of radial spokes. The "optical" part comes from the fact that optical sensors are used to detect motion of the radial spokes.

From the first Macintosh mouse onward, ball mice have used the same basic mechanism.

Well, Wikipedia seperates mice into categories: Mechanical mice, Optical Mice (which includes Opto-mechanical as a type of optical mouse), Laser Mice, and some rarer types. Perhaps "regular" mechanical mice are rare and what I believed where mechanical ball mice were actually opto-mechanical mice?

I think the quote which is confusing you is this one:

"Optomechanical mice detect movements of the ball optically, giving the precision of optical without the surface compatibility problems, whereas optical mice detect movement relative to the surface by examining the light reflected off it."

Put bluntly, Wikipedia is wrong.

The term "optomechanical mouse" means what I said. Here is an example of the standard defintion: http://www.certiguide.com/aplush/cg_...nicalMouse.htm

Theoretically, a mouse using the type of mechanism suggeted by the Wikipedia quote could be made, but I'm not aware of any actual product doing it.

The basic lesson here is to not trust Wikipedia too much.

Here's a video of my Honeywell optomechanical mouse. It's a demo model with transparent shell so you can see the optical part. Wikipedia's definition is the exact one Honeywell's engineers used.
http://4crito.com/video/optomechanical.mov

Thanks for clarifying...guess I will avoid buying optomechanical, seems lots of eBay listings try to use this as excuse to call a ball mouse optical, but then again, the sellers could be confused themselves by the term.