I can game on mine, no lag as a 3rd monitor to do surround in World of Tanks (WoT).
I have a Lenovo Y510P with 2 GeForce 750m cards, and the laptop has 1 HDMI and 1 VGA port, both go to my Samsung T27B350 TV/Monitors running at 1080p@60. I have a Desktop that I actually run 6 of those Samsung monitors with 2 video cards. Since I choose to rebuild my Desktop, I have been using my laptop in the meanwhile. I wanted to use 3 monitors so I could game with peripheral vision, since World of Tanks supports 120' FOV. While my center and right monitors are handled by the laptop video ports, I was short 1 port to do 3 displays. I initially used a KWorld USB2-2-DVI, and that even worked, but there was noticeable lag. Since I only use about 1/3 of the side monitor, this was possible. If I tried to use the entire screen, this might have been bad, but for my purposes and this game, it was acceptable. Since I saw they released USB3-2-DVI, I figure it could only be faster. they were right, now using 1/3 of my left side monitor, and there is almost no lag, I would have to be looking for it to even notice. It works perfect, so this will work in place of the Matrox TripleHead2Go I was looking at. I will try to see how it handles full screen, but for a partial screen, WoT in 1080p is fine.
Hope this helps out someone who is trying to decide if this will work, I think if you wanted to watch full screen videos at 1080p@60 this would handle that no problem at all.