Here's a small change I noticed:
In Leopard, you can toggle the state of an item on the Sync tab of the .Mac System Preferences pane with a tap on the Space Bar. I drag-selected a few entries (Bookmarks, Calendars, Contacts), and pressing the Space Bar would toggle all of them. Also, Option-clicking turned all of them on, and Shift-Option-clicking turned them all off.
[robg adds: This Space Bar toggle feature works anywhere in System Preferences (and potentially in other apps, though I couldn't think of any with list-style checkboxes to test with) for items that are shown in a list with checkboxes next to each item -- the Sharing pane, for instance. It definitely doesn't work in 10.4; you have to click the mouse (as far as I know) to enable or disable a given entry.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20071026142431774