The Elgato Thunderbolt SSD is the first true portable Thunderbolt storage device. Like USB portable drives, it only needs one cable for both data and power. The Elgato could be even more portable, however, if it came with a short Thunderbolt cable of its own. Instead, like all Thunderbolt storage devices I've seen, it doesn't come with any cable, forcing you to buy the 6.6-foot long cable from Apple, which is bulkier than the drive itself. The Elgato is also very expensive; it costs around $700 for 240GB, and $430 for 120GB.
The Good
The Bad
The Bottom Line
To the device's credit, it does host a solid-state drive on the inside, which is already very expensive. In my tests, it offered faster performance by far than any other bus-powered portable drives. Since Macs generally don't offer USB 3.0, it's basically the only option for a fast and portable storage solution. So for those who have the funds, the Elgato will deliver.
That said, unless you absolutely need a very fast storage device, you might want to get a USB-based portable drive, which costs around 10 times less for the same amount of storage space.