I'm very pleased with most of vMix's interface, but there's one thing i thing could be improved: when manually moving the mixing slider, A and B sources stay the same until you reach the right side, then they will immediately switch, releasing the mouse's hold of the slider. I'd prefer the switch to occur only after i release the mouse button at the right end, so that i could easily transit back to the previous input without having to "grab" the slider again.