The QEMU PowerPC emulator is very temperamental.  The highest known-working
version for my PowerPC VMs is 1.0.0, but even this version requires a ROM
(openbios-ppc) from a previous version (0.11.1) in order to boot.  The emulator
is also rather slow.

Problems you may encounter include spontaneous malfunction of the NIC driver
(recoverable without reboot if you can reset it somehow, but recurring and
very annoying) and - on some earlier QEMU versions - misordering of IDE
controllers such that IDE targets 0 and 1 show up as hdc and hdd, and 2 and 3
as hda and hdb.