Mac:
----
1) Moved installed files on a Mac to the Application Support folder instead of installing them in the root folder.
2) Harmony 1000 USB Drivers are now "silently" installed and configured on a Mac 10.5 so that the user will not have to configure them manually.
3) Installing the Harmony client software on a Mac "Case-Sensitive" OS is now supported.
4) A system restart is no longer required after the installation of the client software on a Mac.
5) New "look and feel" for the Mac installer
6) Mac disk image size reduced by half compared to previous releases.
7) Built-in Mac uninstaller utility.

Windows:
-------
1) C:/documents and settings/$user_name$/Application Data/logitech
-This folder contains preferences files and cookies

Upon opening the Harmony client the other day, the software automatically upgraded to 7.4.2.1. It does look like the latest you can download is still 7.4.1, though. This new version fixed a sync issue with my Harmony 880.

Obtained by update in the software (not visible on website)