Down at the Dock, the behaviour has been changed a bit. Menu options have now been consolidated and given a more iPhone OS look:
The new look Dock options
A long click on a dock icon in Leopard brings up a menu. In Snow Leopard, it activates Exposé's Application Windows feature. Whether this is quicker than moving the pointer to a corner or smacking a function key is debatable. But I know new users who are still perplexed by the Dock, and they may find it useful.
Using Expose from the Dock
Hold down Alt while clicking, and you get slightly different options:
In any case, with the feature activating in less than a second, it's easy to stumble upon, and that's the biggest headache for any software designer: getting people to try something potentially useful. After noticing the new option, I got the habit, and the habit stuck.
And to encourage Exposé use, there's the new choice of where minimised windows end up. You'll find this in the Dock Preferences:
Minimise to the application icon - in the left-hand side of the dock - reduces clutter on the Dock's right-hand side
Speaking of Dock curiosities, I don't know why the Apps and Docs folders show as folders, but the Downloads "as Stack". Presumably, it's to show right up that docked folders can be displayed in a choice of ways.
I discovered that I could open multiple applications from a Dock folder using Cmd-Alt-click, with the folder remaining in the foreground.