I am still not using Exposé to its fullest, I guess. The leap from ion is quite big, and I don't like that my desktop gets cluttered regularly. I feel that I have to shove around windows with the rodent too much.
With ion, that was simply not an issue, to the point that I did not notice for hours when my mouse was occasionally inoperational (switching between Trackpad and USB mouse after hiberation went wrong in rare circumstances due to driver issues).
In my current working mode, I use Exposé mostly during drag-and-drop operations, when the target window is partly or fully hidden by other windows (start dragging, activate Exposé with F9, move mouse over target window, press Space to select it).
I do not find myself using it to find windows in the desktop mess. For that, I mostly use the Dock, and I hide or iconize windows often. I also use virtual desktops (VirtueDesktops) to counter the mess, but the way the implementation operates irritates me mostly (later more on that).