I have used the old 20GB version (called Phototainer) for over 2 years now with a D100.
In general, I have been quite pleased with it but occasionally, the thing could be a bit temperamental. When copying from a CF card, it would hang over and over again. Normally, you just slide the card in, press the Copy button et voila. However, I often had to manually select the photos on the card and then Copy / Paste onto the Phototainer's hard disk. Last year, I even had to resort to plugging it to a laptop to copy the images, which sort of defeated the purpose ! However, since upgradiung the firmware, it has been quite stable.
For some reasons, it is very quick to display NEF files, but very slow for JPGs.