Homebrew PCBs

Thanks all for what turns out to be a lively dicussion.  However, as a 
follow on assuming that I have backlash compensation (by whatever 
means) Do you know of anyone using an optical mouse as a linear 
encoder?  They way I figure it is indeed possible to communicate to the 
ps/2 port and optical mice have resolutions in the 400lines/inch (some 
much better).  

Has anyone used an optical mouse for postion sensing?

Mike