I'm used to hotkeys for ability use, and needing to use the arrow keys detracts from the default skill keybindings which are nicely placed. I'd love to move the x,y plane by edge-scrolling. No need to change the z axis scroll, I like using the mouse wheel for that.
For the middle button x,y plane scroll you need to allow an alternate scroll configuration...ie instead of moving down while the middle button depressed scrolling the map up, moving up scrolls the map up. Basically offer a reverse configuration. If thats already in, I'd love to know how to get to it.
Once I got in the rhythm the middle button scrolling worked better than edge scrolling for fast action and escaping, so I really like that use. particularly since it frees the left hand for skill use, messaging, etc.