I am surprised it is missing a horizontal scroll wheel- although it could be programmed to use the vertical wheel in combination with another button. Does Apple have some kind of patent coverage on the little trackball scroller? I use that for horizontal scrolling in spreadsheets quite frequently.

I generally find buttons and other physical controls much more usable than touch style interfaces and would be willing to give this device a try to see how it compares with the Space Pilot. http://www.3dconnexion.com/spp/index.php