I've also been experimenting with considerable success to use a CF bluetooth card for PAN networking, using the following entry in networks:
iface bnep0 inet static
gateway 192.168.100.1
broadcast 192.168.100.255
netmask 255.255.255.0
address 192.168.100.2
#pre-up cardctl resume
#pre-up sleep 1
pre-up pand --connect xx:xx:xx:xx:xx:xx
pre-up sleep 1
post-down pand --killall
#post-down sleep 1
#post-down cardctl suspend
the commented out lines were my experimentation with leaving the card suspended - when I plug it in, it automatically turns on whereas I'd prefer to keep it suspend when not in use.
My only problem seems to be that when I've used wlan0 and bnep0 that the Z doesn't suspend any more... in fact, its behaviour gets very odd, it kind of half suspends - screen blank but backlight on with cursor top left, then un-suspends and wifi turns back on again!