I can only say that I wouldn't use my A1200 without the Mediator anymore. It's great that Amiga users can use cheap PCI expansion boards, instead of buying expensive Zorro graphics and sound cards etc. A great piece of hardware, eventhough I don't like their towers, but that's another issue.
I'm happy about my mediator, and have also bought one for my A4000. As mentioned you get 7 zorro slots, so you are still able to use your old zorry slots.
Regarding the support, I can't complain. With some of my small problems I have received emails answering my questions even on a sunday afternoon. It's more than I expected.