I have been quite pleased with the portable hard drive I've been using for a couple of years now. With my D1X, I could get around 45 NEF files to a 512MB card, and it took right at ten minutes to download the card into the HD. Except in the heaviest shooting situations, I rarely had to use more than 2 cards - one in the HD and one in the camera. Today, I took the D2X for its first real nature shooting spree. It puts about 49 NEF files on a 1GB card and the card takes at least 20 minutes to download (these are Sandisk Extreme IIIs here, so the read speed is pretty high). It wasn't long before I had 4 cards waiting in line for downloading and it took nearly an hour and a half to dump them all. The HD dumps into the computer at home much faster, so I'm guessing the read speed of the cards is the limiting factor. And that will also put the battery in the HD to the test. That's the weak link to any HD I've ever studied. Even the best ones last for only a fraction of the drive's capacity - usually no better than 1/3. I guess theoretically I knew that would be the case, but geez....... Now I have to decide whether to buy more cards or another HD so two can be running at once. If I was near a power supply, I guess I could opt for the wireless transmitter to my laptop, but those plug-ins are hard to find in the boondocks. Sigh.......the problems with advancing technology.