The Lync 2013 client update is comprised of two separate updates, lyncloc2013-kb2760512 and msores2013-kb2767852. Both updates are available in x86 and x64 versions.
Now that Lync 2013 is an Office component, the version you chose should match the version of Office 2013 you have installed. If you try to install the x64 version of an update when you have the x86 version of Office installed, you'll get an error:
|Wrong Update Architecture|
The update requires a reboot. Once you login to Lync 2013 you can go to Options > Contact List, where you will find a new option, "Show contacts with away, offline and unknown presences in a separate group".
|Lync 2013 Options > Contact Lists|
This option is defaulted to off. When you turn it on Lync 2013 creates a new dynamic group at the bottom called "Away and Offline Contacts". Anyone who is not available at the moment is moved to this group. Your other groups only contain users who are online, as shown below:
If no one is online for a particular group, the group shows (0) members. Pretty cool!
Another new option is the ability to select which client Lync 2013 uses for meetings -- The Lync 2013 desktop client or the Lync app from the Windows App Store.
Here's the Lync MX client that is available from the App Store.