> Is there any decent way to get out of the boot program after shutdown?

What do you mean here? If the booter has already begun the shutdown sequence
then MacOS is pretty much ready to get kicked off the machine.

I believe the idea behind the booter is to do the following:

1. Insert a shutdown event that gets executed at shutdown time.
2. Shutdown MacOS to quit all programs and have MacOS write all unwritten
   data and close down nicely
3. Run our shutdown event which hoses everything starting at Memory address
  0x0 through the size of the kernel with the kernel image
4. jmp to the boot address of the kernel

Pressing Cmd-Period should be good all the way through part 2. After that,
there's no OS in town until NetBSD starts so unless you can program the
machine by flicking the debug switch... :)

> Command-Q won't do it; neither will any other combination I could think of.

Ctrl+Cmd+Power will do it :)

> It isn't nice to the Mac OS to just shut the machine off...

So long as it runs the Shutdown sequence and it gets to write everything it's
caching to disk you can shut the machine off or whatever you like.