The TEAC installed instantly on my testbed 3.0GHz Pentium 4 Gateway PC, registering as a Toshiba MK8026. It comes pre-formatted for use with both Mac and Windows machines, which is both good and bad if you intend to use it for storing large video files: because it's pre-formatted as a FAT32 drive, it comes saddled with FAT32's 4GB filesize bodice. If you expect your filesizes to exceed 4GB (like if you're capturing uninterrupted DV streams of more than 20 minutes), you'll need to re-format the drive as NTFS. But theoretically, if you leave it as is and intend to use the drive interchangeably with both Mac OS and Windows systems, FAT32 is your friend.
At 5400RPM, the TEAC 2.5" isn't quite state-of-the-art for external hard drives (today's fastest are 7200RPM), but 5400 is typical of what you'd find in your laptop's internal drive, and generally fast enough to capture video directly to the drive if that's your goal and to accomplish large file transfers and backups without unexpected delays. A 2.8GB DV-AVI file transferred from the Gateway's internal Maxtor 7200RPM SATA drive to the TEAC in a brisk 1:59. The same file copied to a 7200RPM LaCie external USB drive in 1:51. 154MB of files of assorted types and sizes copied to the TEAC in :19; the 7200RPM LaCie clocked in at 18 seconds for the same fileset. The copy times were virtually identical for the Maxtor-to-TEAC copy functions as copying the same files to alternate locations on the Maxtor internal. For more advanced backup functions, the TEAC ships with the bundled version of NTI's industry-standard BackupNOW! software solution.
One of the advantages TEAC also touts for its portable HDDs is the ability to add "unlimited storage" with multiple portable drives of varying capacities. While not an entirely empty claim, since the drives' compact construction certainly leaves bandwidth for carrying more than one at once, you can't daisychain these drives as with many external drives (both magnetic and optical), and it's hard to imagine why you'd want to anyway since they run on bus power. While we didn't have multiple drives to test, it wouldn't be unreasonable to surmise that you'd take a performance hit connecting multiple bus-powered devices to the same USB bus on systems with USB cards that include 2-4 ports.
That said, the TEAC HD2U-80 is an excellent portable storage accessory that delivers solid capacity for an external hard disk drive at a $269 price tag that's more than justified by the drive's performance and compact construction.