[font color=\'#000000\']I have owned 1G MD's (IBM's) as well as currently own a 4G Hitachi and found them very reliable -- even after dropping them on occasion.
However, the 1G versions seemed to use more battery than the CF cards in my 1D so I sold them -- probably not a huge issue in a MKII.
FWIW I now use the Hitachi 4G in my Contax 645/Kodak digital and have had zero problems, though I do believe the CF cards are less prone to impact damage than MD's so I prefer CF's for my MKII and 1Ds.[/font]