I've been using an MXI Security Outbacker MXP for a few months now, and although I generally eschew portable storage devices (usually since I have a nasty habit of losing the power cords, if not the actual device itself), I like this one.
At it's essence, it's a 1.8" 20GB drive with a fingerprint scanner built into the case. When it's powered up or connected to a USB host device, an LED blinks on the case, and either the drive is not visible to the host system, or only a public partition is available, depending on the configuration. Once a valid fingerprint is detected, however, the secure partition is made available to the OS.
This split personality is a nice feature, since you can store non-sensitive info on one partition and use the other for private data. The only problem I faced is that the device requires a Windows system to configure the partition settings and enroll fingers for access to the private partition. Once the configuration is done and one or more fingers have been enrolled, you can access and format any partition as you wish, with ext3, NTFS, UFS, or what have you. The security aspect blocks access to the secure partitions, but doesn't affect otherwise normal operation.
Another nice feature is that the control software for configuring the device is housed in a small read-only partition on the disk itself. If you lose the accompanying CD, or simply don't have it handy, you can still hook the drive up to a Windows system and run the configuration tool, assuming you have your fingers handy. Additionally, the device can be powered exclusively from the USB port on most laptops.
So all in all, it's a good solution for carrying around sensitive information, especially if your laptop doesn't offer biometric security. And I'm happy to say that I have yet to lose it.