I was in a hurry to leave.  "I'll just check this with the debugger, and I'll be out of here" I said to myself as I plugged in the 1394 cable, connecting my dev box to a new target system.

Two quick commands to the bootcfg utility on the target machine:

bootcfg /copy /id 2 /d "1344 DEBUG"
bootcfg /dbg1394 on /id 3 /ch 30

I was just about done.  "Let's see... Start... Shutdown... Restart!" -- I was mumbling to myself as I rebooted the target system and swung around in my chair to fire-up WinDbg on my dev box. I looked at my watch. "Damn, I should have left ten minutes ago," I thought, "but it'll just be another minute now."

But when the target system restarted, it was as slow as molasses. Not just slow, mind you, but painfully, glacially, horribly, slow.  Like, it takes minutes to get to the login prompt slow.

Reboot.  Same problem.

"Chin!" I cursed to out loud as I remembered what I had done wrong.  I had forgotten to disable the 1394 host controller driver on the target system!

Debugging over 1394 is rock solid.  Really.  If you find that you're having problems with 1394 debugging, be sure to check that you've disabled the 1394 host controller driver on the target system (go into device manager, and just set the driver to disabled).  The problems you can see will range from very slow performance (what I was seeing) to lost debugger connections.

Oh yeah.  And never rush trying to do "just one quick check with the debugger."