bob> I'm having difficulty booting my PDQ Powerbook (300 MHz G3, OF 2.0.1)

bob> pci@80000000/ata0@20000/disk@0,0.  What boot command should I be using?
I don't have particular knowledge on your machine, but in general,
OF 1 or 2 machine will boot with
  boot boot-device 
In your case, that will be
  boot /pci@80000000/ata0@20000/disk@0:0

Did you tried that ?
Also check the listing with devalias at OF.
 If you got 
ata /pci@80000000/ata0@20000
  boot ata/disk@0:0
hd  /pci@80000000/ata0@20000/disk@0:0
  boot hd:

might work,
Makoto Fujiwara, Chiba Japan
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http://www.ki.nu/software/NetBSD/iBook2/