Bought this item for a Mac to save having to keep a spare PC lying around for connecting to serial consoles. Doesn't work out of the box and only comes with Windows drivers.
However, booting NetBSD or Linux within Parallels shows this is a bog-standard Prolific 2303 chipset, for which there is good support. Simply download the OSX driver from Prolific's website and it correctly shows up as /dev/tty.usbserial which you can then attach to with "screen /dev/tty.usbserial 9600".
While it may not be possible for them to include the Prolific drivers on the bundled CD, they could at least provide this information for people who would not know how to find out what chipset is being used.
In the end though, it's still worth 4 stars as it's using a standard chipset so has full support across the board, and is reasonably priced.