If I still had the box, I'd return this. But I haven't, so too bad. Excellent delivery from Amazon, who are in no way responsible for this.
Like a previous reviewer, plugging this in to my Dell laptop's E-SATA port shows a SATA-2 disk only to be working at SATA-1 speed. Just to be sure it wasn't an anomaly with my particular disk (Seagate Blue), I borrowed a colleague's Samsung 830 SSD - and got exactly the same problem.
Startech don't want to know - I raised this with their US Support, who had never heard of the problem before - and alleged the issue must be with my drive. Not so.
Disappointed. I've since ordered an ESATA cable with power for about a fiver, which my colleague with the Samsung SSD uses. Plugged that in, connected my Seagate and it immediately saw it as SATA-2. This cable costs just over a fiver - search for Wentronic 0.5m HDD Power eSATA Cable eSATA I-Type to SATA HDD Plug.