Open the Keyboard Viewer. Click the Zoom/Maximize button. Compare to its “zoomed” size under Panther. Thank the person responsible.

(of course, to reach this point you must first open System Preferences and select the International preferences, switch to the Input Menu tab, and check the Keyboard Viewer palette and “show input menu in menu bar” boxes; only then will you actually be able to use the Keyboard Viewer. I think this is one of the most convoluted methods of enabling an essential utility yet devised, and I can only hope that Apple moves the damn thing into Dashboard real soon now.)