I've got an after market focusing screen.
Specifically this one "Rule of Thirds" split image microprism focusing screen for PENTAX K-7. .
Who else uses alternate screens?
I like the split prism for manual focus!
My 1977 vintage MX has one and I have one on my K20D as well.
FYI There are three main alternates that I've found:
b) Focusing Screens
c) Other eBay cheapies
So what are your experiences?