After my initial test with ZFS on Mac I had put away the drive I was using as my testbed. I unmounted and unplugged it to do more testing later.
So later on, I decided to remount the ZFS drive and try other things with it. I was still using the IDE/SATA-USB bridge, like I mentioned in my earlier post. As soon as I plugged in the USB cable into the Mac -- *BOOM* -- immediate Grey Screen of Death and the machine was instantly locked up and required a hard reboot. Oops.
Kind of puts a damper on trying a Mac-only solution. I'll try again later when I have time. Maybe it was a fluke?