I installed firmware TR12-TR_06_00_00-7 on my Z3100ps GP. I am using the PS and the PCL3 drivers installed from the August GP installer version 3.3.1 (as far as I know, the latest available). I am using Mac OS X 10.4.10.
I am able to create custom papers in the printer using the printer utility as before, with the advantage of the now "built-in" media presets such as Fine Art Pearl Paper (less ink). This allows more than one custom paper that uses the same *custom* media preset (impossible with previous firmware unless you used a built-in HP media preset, or just simply re-linearized the printer every time that you switched papers that shared a common media preset).
However, the problem that I'm having now is when it's time to print, I cannot select any of these wonderful custom papers that I so carefully created. ---- In the Mac OS print dialog, the custom papers are listed on the pop up "paper" menu under "custom", but the entries are "greyed out" and NOT selectable (the HP papers types remain completely selectable).
This makes it actually impossible to print with any defined custom / non-HP papers.
I had to downgrade to the TR_04 version just so I could print again.