After the device is plugged in the udl kernel module is loaded and a new framebuffer device is created (/dev/fb1 in my case). Using mate-display-properties I'm able to configure the 2nd monitor attached to the USB video card. I was able to succeffully display an OpenOffice presentation on the 2nd monitor and play YouTube video.
All USB 2.0 devices from Plugable should be well supported on Linux. For USB 3.0 David Airlie from Red Hat is doing some reverse engineering but I have no idea what the status is. For more info see: