Version 4.0 for Android does include the option to create groups for your contacts, and it also offers a new option to forward a message to another contact. Taking advantage of Android-specific features, there is also a new option which allows you to place a shortcut on your homescreen that will take you directly to a specific conversation, which is pretty cool.
However, the big addition for Android users is voice calling to phones. This is a feature that started on iOS, testing first in Canada and expanding to U.S. users back in January. Now, Android users can also get into the fun. It allows for free calls to phones over Wi-Fi, and calls are also available over mobile data, but of course data charges could apply there and those are only available between Facebook users.
Download: Facebook Messenger