I bought one to see if it worked with a 320GB WD Scorpio Black 7200 spin drive and my laptop with eSata running Vista 64. Worked first time without any issues, great speeds at copying files on the WD drive (averaging about 75-80 MB / second).
Have bought another one of these and the Scorpio Black as an ultra fast alternative for portable storage.
If you've no eSata then you can fall back on the USB (speeds with a Scorpio Black using USB are around 20-25 MB second).
Purchased in order to clone existing 120Gb laptop drive and replace with a new 320gb WD 2.5" (also available from Play). The caddy is of sturdy aluminim construction and is almost idential to the type used for a Fujitsu Handy Drive I already own. The drive is fitted easily and the slots inside the caddy without any problems and is tightended in place by two small grub screws (handily 4 are supplied along with a screwdriver). The drive has USB or eSATA ports. One USB cable provides both power and communication for the drive, which is ideal. I cannot comment on whether external power is needed if the eSATA cable is used as I have not tested it.
The cloning worked perfectly (Acronis) - I swapped the larger drive into the laptop and fitted my old drive into the caddy as a backup location.