Just tried this and may not be news to many, but I FILLED a 512MB SD and TRANSFERRED (within Z) the data to the 4GB Microdrive and it took about as long as the Notebook PCMCIA->SD from HDD in windows XP (give or take a miniute, wasn't watching really close).
Anyway, took about 10 minutes of transfer.
# su - root
# cd /mnt/cf
# cp -r ../card/* .
This is good to know becuase (on my old 5500) I tried a transfer froma slow 128MB Sandisk CD to my Lexar 256 SD and it took FOREVER...like 30 minutes. (yeah,I know 860 has 200Mhz bus, thanks)
With this C-860 transferring this fast, it makes the Z/4GB Microdrive a nice storage utility when you bring your SD camera on a long trip and need to dump off files. BTW, I HIGHLY recommend the Canon SD10 as it takes 4MP pics 320x240 awesome video (3 mins worth at a shot) which on a BRIGHT day can be stretched to 640xx480 with almost no jaggies (at least that is me, I am no videophile) Con is no optical Zoom, but digitial zoom (which I always hated) really works well on this, and it is Smaller and Lighter than a pack of cigarettes....just the thing to lighten the load when carrying a Z around as well.