eWeek's David Morgenstern is skeptical of Microsoft's ReadyBoost and ReadyDrive technologies. These are Vista capabilities that allow flash memory to increase apparent RAM and speed boot times respectively. As far as ReadyBoost goes, I agree: the idea of depending on a USB dongle to increase RAM seems very hinky to me. There's an enormous step down in access speed from RAM to Flash and Flash memory can wear out (MS surely uses the algorithms that mitigate, but not solve, this issue).
ReadyDrive, on the other hand, I quite like. This is the idea that your hard-drive will have some integrated Flash in which it caches boot information. This time, there's an enormous step up in speed from loading a driver from the hard drive to loading it from Flash (especially if instead of actually loading stuff, you're just bltting the in-memory image from Flash to RAM). Morgenstern points out the orders-of-magnitude disparity in mean-time-to-failure between Flash and hard-drives, which may be valid, but I wonder if both don't exceed the reasonable operational time of a drive.