I never drop any of my hard disks before, but I have RMAed dozen of hard disks in the past few years. :think:
May be becos of all these bad experiences with hard drives, I never trust microdrive, especially if I have to carry the MD around, and may need to swap the MD when it run out of space, no way that I will take the risk.
To save time when I have to change CF, I just dump the filled CF inside my pants/shirt pocket, and wait till I am free then I will keep the CF card in a safe place. No way I will want to do that to a MD.
With the large buffer found in MKII, I feel that there is no need to get high speed CF, I don't understand why one shouldn't get MD because of 8.5fps (unless he got the same reason as myself). Since the buffer is large enough to hold more than enough photo that most pple will shoot, so even you have the slowest CF/MD, it will not affect your shooting because the buffer should clear faster than you can fill it up, therefore the write speed is not important.
Unless you are those who review your pic more than you shoot, then a fast CF may be useful. Otherwise, IMO, it is not worth to pay extra for high speed CF when MKII don't really need it.
This analysis is based on MKII only, for other cameras, high speed storage device may help, take for example, your 300D.