The biggest visual change is a complete revamp of the opening 'Overview' page, with much more status information clearly displayed.
|The new Overview page|
The other big and very welcome feature is the addition of Guest Wifi Access. This lets you setup a separate Wifi network (2.4GHz only), with its own security. It uses a separate subnet to the main Wifi network, so users can't access your home network, just the internet.
|Guest Wifi Access has been added|
Another welcome feature is the return of MAC cloning, something I managed to convince AVM was still something of great use to many users outside Germany.
|The return of MAC address cloning|
Power consumption should be improved slightly by the addition of a Green Ethernet function that turns off power to unused ports. [UPDATE 4/1/11: No, it doesn't - see this post to find out what it really does]
|Green Ethernet function|
The international version of the firmware can be downloaded via the Fritz!Box's automatic update tool in the System menu. The full list of changes can be seen in this text file