According to the release notes, the update comes with a number of improvements, including the long-desired ability to send function keys and system shortcuts (Force Quit, cmd-Tab for application switching, cmd-shift-Q to log out) to the remote Mac; previously those commands would execute on the administrator's machine, which could cause undesired behavior. Also included are support for wide-area Bonjour connections and improved performance when using a shared screen.
If you're just starting out with ARD, be sure to check out some of the great tutorials Apple has posted online. From getting set up, to providing remote assistance to users, to automating routine tasks; as Apple might say, "there's a tutorial for that."
Thanks to TUAW reader Jim for giving us the heads up!