I considered microdrives when I got my Canon 10D. I ruled them out for a few reasons.
1. Moving parts fail.
2. Moving parts die when you drop them.
3. Moving parts need more battery power.
4. Moving parts are slower than memory chips.
(consider your PC's memory vs. accessing the HD)
The only MD advantage is price & maybe not that if you drop stuff often.
I decided on SanDisk Ultra II (read 10MB sec write 9MB sec)
& never gave MDs another thought. Of course we're not talking video with a 10D.
It's a little old but here are some
speed tests for CF cards including IBM MDs.