Ok, I'm putting my cognitive scientist hat on. There is an issue of metaphors here. I do not mean metaphors in an English literature sense, but rather in a cognitive sense; directed blends from an abstract domain to a concrete domain. There is a fair amount of evidence that everything abstract we think about is given its meaning and reasoned about through metaphors.
Every layer of indirection means that the unconscious mind (the vast majority of the mind in any human) has to work that little bit harder and increases the risk of misreasoning. A finger, or a paint brush, are less indirect than a mouse (the motions of the mouse do not correspond with the observed effect, etc.). The harder the brain has to work, the more likely that consciousness (a slow, blocking process to abuse computer science analogies) has to get involved to sort out error conditions. This leads to an overall slower thinking process, less creativity and makes the interface mentally more tiring.
Final Cut Pro may seem efficient, but it is efficient up to the maximum allowed by the interface method thanks to this indirection. A replacement interface (and I can think of several right now, but then I've been designing multitouch mockups since before the iPhone and video was one of the examples that interested me as being ideally suited to this sort of UI) may start at a lower efficiency. It would, however, have a higher ceiling than the existing method. It would not, however be Final Cut Pro. It would be something just as capable, or more so, but with a very different way of looking at the problem. What is wrong with that?
