Guys, it is possible to get Displaylink working as a third monitor but you get degraded performance. (lag) You need to download the 3.10 kernel.http://linuxg.net/how-to-install-kernel ... derivates/
I have an Nvidia driver which failed right out of the box so I had to go install the Noveau driver from "Device drivers" located within System Settings. After a reboot go under "Displays" and configure your three monitors and they do show, but like I said the performance is severely degraded. When I just had my 2 19inch monitors everything works perfectly. Adding the third is where it fails.
I've been playing with it the last few hours with my Mint 15 installation and trying various desktop environments but they all suffer as far as quality goes. I tried Razor-QT, XFCE and even Openbox with no luck. The closest I came was Razor-QT but as soon as I launched a movie on my third monitor (which is a 37 inch TV) my picture was garbled. If you plan on using 3 monitors the same size you may have luck. Go to the link above, follow the download instructions, and like I said your proprietary Nvidia drivers will fail out of the box (not sure about ATI/AMD) so install the Noveau and then try different desktop environments until you find the right combo. Let me know how it goes. Maybe I can get my system working.