My understanding is it behaves exactly like a Sun Type-7 Unix Keyboard (there is also a "PC" version, with a slightly different layout).
Well the Sun Type-7 Unix Keyboard does work - with a couple of reservations.
The CAPS LOCK light doesn't (light that is). The COMPOSE light doesn't work either. The COMPOSE key does work properly, as does CAPS LOCK (only the lights fail). The SCROLL LOCK and NUM LOCK lights work correctly. The USB concealed connector works with a Sun Mouse (this is plugged in directly not via a USB Hub). I've not tried the other USB sockets (I imagine plugging things in there could well catch-up to what the Raspberry Pi can supply, power wise). The Sun "special" keys don't do anything useful.
However it works "well enough". I selected "Sun Type-5/6" from the initial config. Mine is a "Unix" type but I have no reason to suppose a "PC" type would be different. Mine is also "US" layout.
Selecting "Happy Hacking Keyboard" stopped the COMPOSE key from working - so they are a little more different than I'd thought. Unfortunately I don't have access to a Happy Hacking Keyboard to try...
Anyone else got any experience?