I suspect that the Sony micro drives are just like the Hitachi ones. In fact Sony may be licensing them from Hitachi (Hitachi bought the rights from IBM). I have one of the 2gb Hitachi drives, and 1 of the 1gb IBM Microdrives, and several other CF cards. The microdrives are considerably faster than any of my CF cards. The Hitachi is much faster than the older IBM version. I bought the Hitachi 2gb drive for $69 after a rebate, so they are very cost effective. But I'm seeing some places sell a 4gb Sony for $150, so the price on all of them has dropped. Some people are afraid, that since they have moving parts, that they may not be as reliable as the regular CF cards. I've been using the IBM one for 4 years and it still works like a champ. Keep in mind that you can't use them at elevations above about 7500 feet, so that can be a drawback if you are a climber or shooting from a airplane or copter.