I bought a D1X the week they were launched in the UK (June last year) and purchased an IBM 1gB microdrive at the same time. I was concerned with using a microdrive due to the my knowledge as to how the technology works (I am an IT professional) and how easily the head of the disc assembly can be forced onto the disc surface rendering it useless. However, it must be said, that having used it solidly for 9 months and shooting literally thousands of images, it has not let me down once. I hasten to add that I do not generally treat my equipment with kid gloves (which is why I chose Nikon equipment in the first place).
Having said that, I am a realist and I believe solid state compact flash cards are the way to go both for speed and more importantly, reliability.
I gather there are a few company's out there producing 1gB cards although the price is much higher than the microdrive (in the UK, where I live, you can expect to add about 50% onto US prices for the same item!!!)
To summarise, by choice, I would now go for CompactFlash cards and that will undoubtdly be my next purchase.