I like most of the new features in Leopard (yes, I even like the translucent menu bar!), but there are as always small annoyances.
One of those annoyances is that the printer application stays open and in the dock after printing.
Fortunately there is an easy solution:
Next time you print something just right-click and select “Auto Quit” from the menu:
Voila – now the printer application will quit after the job is done.