i dunno if OS4 supports the mediator? but it could be a way of re-vitalising any PPC expanded classic machine?
otherwise, if you can, get a deneb USB card. USB lan adapter, usb sound card, usb mouse, usb hard disk, flashrom to avoid reboots. all on zorro3! sounds good to me! :-)
Yes, OS4 does support the mediator. The OS4 native drivers won't support any pci cards that rely on the graphics-card DMA hack. However, you can use the drivers that come on the Mediator's CD (so long as you use all Mediator drivers for PCI devices).
Personally, I think that OS4 is worth getting.
Hans