I have to support a USB video devices at work, various types of them, for laptops that do not have a docking station. Im not sure how well they would function on Linux, but I wouldnt suggest them to anyone. Because they are USB, the more data they pull over the connection, the more work the CPU is burdened with.
They are also rather laggy. it isnt very apperant if the only display is on it, but when side by side with a standard display (like the laptop monitor) it is extremely noticable. For UI1, I think it might be doable but I wouldnt expect UI2. Video playback might also take a bad hit the higher the quality you go.