[zwerdlds]

It's been a while since I used these UIs, but usually what happens is you click on the knob and it turns into a vertical slider. Not so bad really.

The skeumorphic UI lets you move between the physical panel and the GUI pretty seamlessly. Not saying there isn't a better option, but this at least is pretty nice for beginners.

[dkersten]

Except for a few emulations of hardware, most of these UI's don't correlate to a physical panel and the lack of consistency between the various virtual-only ones, IMHO, negates any benefit from a consistency point of view. Having something look like a physical knob is one thing, but when each plugin you have has its own different style of "physical knob" design, I find it gets messy personally.