From another review...
In a few months, most distros should have the patch to the Linux kernel driver that makes this a friendly, no-hassle plug-and-play experience. That's when I'd give this product a full 5 stars.Else, if needed, just create a file /etc/modprobe.d/medialink-btusb.conf and put this one line in it:
install usb:v0A5Cp21E8d*dc*dsc*dp*ic*isc*ip* /sbin/modprobe btusb; echo 0a5c 21e8 > /sys/bus/usb/drivers/btusb/new_id
Detailed explanation: This device is handled just fine by the stock btusb kernel module. The issue is that the driver does not recognize the exact USB vendor/product ID. However, the driver was fixed just a few weeks ago. It'll just take a little time for your favorite Linux distro update to pick up the fix.