Here's an extension to this functionality that makes it even better.
Take the existing applescript:
tell application "Finder"Save this to a file in your ~/scripts folder under a name like "refresh.scpt".
tell front window
update every item with necessity
Use the application Quicksilver to assign a trigger and key combination to the script and you can use something like "Command-R" to refresh the window - works beautifully.
You can find Quicksilver here (link: http://quicksilver.blacktree.com/).
Thanks to the original poster of the applescript: Eric "Heavyboots".