I'm seeing a fair number of panics such as:

 panic: lockmgr : locking against ...
 at netbsd: cpu_Debugger+0x10: lw2 r0,r1,0x14

 panic: mp_save_fpu_proc
 at netbsd: cpu_Debugger+0x10: lw2 r0,r1,0x14

NetBSD 2.0C (GENERIC.MP) #0: Mon Apr 12 13:55:46 CDT 2004
        build@enki:/opt/obj/macppc/opt/src/sys/arch/macppc/compile/GENERIC.MP
total memory = 448 MB
avail memory = 424 MB
mainbus0 (root)
cpu0 at mainbus0: 7400 (Revision 2.9), ID 0 (primary)
cpu0: HID0 8094c0a4<EMCP,DOZE,DPM,EIEC,ICE,DCE,SGE,BTIC,BHT>
cpu0: 500.00 MHz, no-parity 1MB WB L2 cache (PB SRAM) at 2:1 ratio
cpu1 at mainbus0: 7400 (Revision 2.9), ID 1
cpu1: HID0 8094c0a4<EMCP,DOZE,DPM,EIEC,ICE,DCE,SGE,BTIC,BHT>
cpu1: 500.00 MHz, no-parity 1MB WB L2 cache (PB SRAM) at 2:1 ratio

and with GENERIC on a dual 500Mhz G4

Is 2.0 just not stable yet on macppc?