Here are some of the enhancements included with the Apple Remote Desktop 2.1 Update.
Remote Assistance
Full screen mode: You can now control and observe remote computers in full screen mode, allowing you to view the remote screen on the entire screen of your display.
Control and observe remote computers with multiple monitors: Administrators can now control and observe remote Mac OS X systems which have two or more displays. The displays are shown in one virtual window.
Support for mouse scroll wheel and right-click when controlling remote computers.
Improved control and observation of remote computers that are running applications in full screen.
Improved opt-out for Guest Access option.
Improved support for third party VNC Viewers and VNC Servers.
AppleVNC Server no longer relies on presence of mDNS process.
Remote Administration
Multi-line output for Send UNIX Command: You can now view all the results from the Send UNIX Command.
The Install Package command now detects whether a package requires a restart and will optionally restart the client computers after the package installation has completed.
Send UNIX Command no longer dependent on client side Observe privilege.
Asset Management
Improved printing of hardware and software reports.
Improved remote data collection.
You can now drag results from reports to the Finder. The items will then be copied from the client computers to the administrator's computer.
Software Distribution
Improved file copy for files that reside on networked home directories.
Other enhancements
Client authentication using Active Directory: Clients can now be authenticated against directory services groups in Active Directory.
Improved client authentication using two additional directory services groups, ard_manage and ard_interact. Members of the ard_manage group will be able to perform all commands except for Control and Observe. Members of the ard_interact group will be able to perform all commands under the Interact menu.
Enhanced column sorting in the Administration application.
Improved support for managing computers that have Dynamic DNS enabled.
Administration application now correctly remembers it's settings if it unexpectedly quits.
The ordering of network scanners is now remembered.
Includes security fix present in Security update 2004-10-27 (details).