I agree with Cadwell, microdrives aren't as fragile as one would think. I've used the 340MB and 1GB versions. After 3+ years, I still have and use (sometimes) my 340MB. However, I find microdrives painfully slow on my 10D. So now, I only use CF cards.
I'd recommend getting smaller CF cards and a FlashTrax (or some other popular portable storage device) rather than many huge GB ones. And I certainly wouldn't recommend getting just one very big one. I use 2 x 512MB cards with my FlashTrax. One card lasts the equivalent of 2 rolls of film. When one is full, I switch to the 2nd one while the first one uploads to the FlashTrax. So far, I haven't shot 72 frames faster than it takes to transfer all the files from the other CF card. Plus, my 40GB FlashTrax is good for an equivalent of 160 rolls of film. So everything works out fine for me.