There are so many great improvements to the Links panel in InDesign CS4 that I missed one cool improvement until I stumbled across it today. You can update a modified link with a single click! Here's how:
When you have a link that has been modified in another program such as Illustrator, Photoshop after it was placed in InDesign, a small yellow triangular warning sign will display in the Links panel.
If you want to update a single modified link, you can now just click on the yellow warning sign, and the link will be updated immediately. You can do this in CS2 and CS3 also, but when you click on the warning sign, it leads you to a dialog box, and it takes at least 3 clicks and some brain cycles to complete the process. In CS4 it is one click and zero brainpower required. Nice.