Please verify that it's bricked

[Febs]

Nope...likely i'm mis-using the label. 'A' isn't the top edge button? That one has always worked as select, and 'hold' for power off.

Let's make sure we're all using the same terminology.  Here's how we label the buttons:

[soap]

This sounds like a power button that is either stuck or broken in the closed position.

Every symptom described from the self-powering to the USB mode still working to the hold-switch behavior confirms this diagnosis in my mind.

[justSteve]

The button itself still has the same feel as always...still feels 'clicked' as all the other buttons. Given that, do I score this one as bricked or look for a guide to opening the case?

thx

[soap]

Just because the button mechanically feels the same in no way comments on its electrical behavior.
I would wait for someone smarter than me to speak up, but assuming there is a short in either the power button, or where it interfaces with the motherboard, opening up the Gigabeat will easily allow you to test the theory.  I in no way, shape, or form would consider it bricked.
However – I will take it off your hands for $25

The real trick in disassembly is removing the top and bottom plastic end-caps without breaking the very fragile clips, which hold them in place.

Once you get that far it is only a matter of removing some very small Phillips screws with a teeny tiny screwdriver.

[justSteve]

Any photos showing what's under the cover. It'd be most helpful so see  how those snaps engage.

[LambdaCalculus]

The MyGigabeat forums seem to have a wealth of information. Here's a thread:

http://www.mygigabeat.com/2005/08/f41-disassembled.html