At any given time, my thumb is on bottom left, pinky on bottom right, index on top left, and ring on top right.
I've got mine so thumb is normal click, pinky is right click, index is middle click, and ring swaps between horizontal and vertical scrolling. I also have it setup so that clicking the bottom two together acts as a "ctrl/cmd+w" to close windows, which is epicly handy when combined with the dedicated middle click button and my love for having a bajillion tabs open.
I use index or middle finger. Palming it would feel a tad retarded IMO (exuse my terminology). It sounds like Jeff uses the ring finger: "ring swaps between horizontal and vertical scrolling."
You're using your wrist FAR LESS than with any kind of normal mouse!
Middle click doesn't need to be used often at all, especially in a DAW setting.
In a DAW setting, no, but I couldn't live without it for web browsing! (opening links in new tabs, that's how I read all the threads with new replies on here!) Also, my chair is low enough relative to my desk that my elbow usually hangs below the desk's surface (with my wrist resting on the edge), so I don't have to deal with angling my wrist back to use the mouse (which I agree can get supremely uncomfortable - fortunate, I suppose, that I'm an epic sloucher )
Exactly, for web browsing it's a godsend.
That said, the angle you're talking about was the one I had problems with - when your wrists are angled downward (elbows below where the mouse would be causes arms to angle upward but wrists to angle downward), you run a greatly increased risk of RSI related injury/pain. Always better to have your elbows level with or a bit above, and have your wrists prone or bent just slightly upwards.