Check out http://www.dpreview.com if you haven't already.

The biggest knocks on the microdrive are 1) increased sensitivity to shocks or bumps, esp. during read/write operations; and 2) increased latency during writes. If you are in the habit of jostling, bumping, or dropping your camera, or will want to shoot shots in rapid succession, you should consider having a flash card at least as an alternative storage medium.