Great tip, although you don't need to place the cursor anywhere special, just inside the Logic interface, including the toolbar and scrollbars. It will always affect whichever track is selected.
It should go without saying, but you need to have a multi-touch trackpad for this to work. Older MacBooks and MacBook Pros only support two-finger scrolling, so this won't work on those older machines. The Magic Trackpad will work as well, but the Magic Mouse won't as it doesn't support rotation without 3rd-party help. Perhaps with Sesamouse it will work, feel free to chime in if you use that combo.
Made a quick screenshot guide as well:
]http://img812.imageshack.us/img812/6504/rotatelogiccontrols1.jpg