Dan,
I've used the metal platen, pyroceram, and leather. Tryied the graphite on someone elses machine.
The metal or pryoceram are for grinding. The cushion is great for blending and handle work.
I have the pyroceram for a long time, until the work rest cracked it. (OK I did it putting the work rest on.) I'm back to metal. The pyroceram is fine but you have to ground yourself to the machine - generates a nice static charge.
(I run the wire into my socket. Didn't have a good connection once. Had a strange feeling in my foot. Like needles jabbing me. I did a very interesting dance.)
Steve