I have been using Greg Schueler’s CornerClick on my iMac. An interesting implementation of Fitts’ Law. While it is true that the corners of the screen have infinite depth, there are only four of them. Using modifier keys is a good way to expand the manipulation possibilities, but forces the user to remember the key combinations. CornerClick used in conjunction with the upcoming 10.3 release with Expose might greatly alleviate the need to use the Dock.