As observed by WC, this update (version 5.5.1277.0 also strips away backward compatibility with Windows Phone 8.0 as Windows Phone 8.1 continues to take over the ecosystem.
Key features of Lync for Windows Phone 8.1 include:
• View shared meeting content during a conference, on your mobile device
• Initiate a group conversation (IM or Video) or invite additional participants
• Join, rejoin and initiate a Lync Meeting to communicate and collaborate amazing ideas
• Control the meeting (mute or remove attendees) and know more about participants’ modalities
• Transfer your calls to another phone-number or another contact
• Pick-up your conversations from the point you ended them
• Join (and enjoy) a Lync Meeting even if you don’t have a Lync account
• Enhanced Security with Lync certificate and passive authentication
Download the new and improved Lync using the QR code above.