I'd be interested not only in a better study of the effect of expertise as well as looking at the effect of this "amnesia" on productivity. Even if it takes me longer to do a task in Emacs, that amnesia suggests that the interface is less distracting, which might be far more valuable than speed.
Reference: http://www.asktog.com/TOI/toi06KeyboardVMouse1.html
Regardless of what the studies say, I often get comments from 'average' users about how fast I type and work. It's all keyboard shortcuts. I remember first seeing a guy using the tab-complete stuff in a shell - I was shocked, because I just thought he was typing fast at first, then he showed me the tab key use. My life hasn't been the same since.
By comparison, when I watch other people use a computer ('average' people), it's like I can watch their thought process as they grab for the mouse, move it around, the sloowly start moving it to a menu, then they click around and move the mouse over each selection, pausing, then moving on. It's painful to watch, and often seems to happen in slow motion.
So... keep the studies going on. Until they study power keyboard users against power mouse users, my money's on the keyboard.
Assuming ViTunes uses a similar set of actions to play music, I could easily see it being a faster way to find and play the songs you want to listen to.
Also, a lot of people compare it to "moving your hand allll the wayyy over to the mouse and back", but I do a lot of coding on my laptop, actually, with my trackpad just inches away from the home row.
I could potentially even learn to use the trackpad with my thumb without even leaving the homerow. I wonder if anyone uses it that way?