Portable hard drives are a commodity product, and it’s hard to make them interesting. Take a notebook hard drive, slap it in a bit of plastic with a SATA-to-USB controller inside, and presto, there’s your drive. If it’s USB 2.0, it’ll read at 33.3MB/s and write at around 29MB/s, and if it’s USB 3.0, it’ll read and write at the speed of the mechanical hard drive inside. Yawn.There’s precious little difference between most external drives, which is why we don’t cover every single one to hit the market. But sometimes somebody does something new. Last month, OCZ slapped a solid state drive in a USB 3.0 enclosure, and it cooked. This time, Seagate’s mixing it up. The new FreeAgent GoFlex drive series moves everything past the hard drive SATA port onto a detachable controller, so the USB 2.0 drive you buy today can, with the addition of a $30 upgrade cable, become a USB 3.0, eSATA, or FireWire drive.