If you are thinking about updating your iOS to the newest Skype for Business client here a list of the features that are (still) not currently available from the previous Lync 2013 version.
If you have auto update enabled, then you might find out a little too late.
• Search your contacts from the Contacts screen.
• Search for Distribution Groups.
• Send an IM to all members of a Group.
• Use Group contact cards.
• Use Call Transfer.
• View Microsoft PowerPoint presentations.
• Set Call Forwarding and Simultaneous Ring options.
• Send the chat transcript as an email message.
• Access a participant’s Contact Card from the Participant List.
Meetings List screen
• Visually identify meetings that are currently in the Tentative acceptance state.
• Access the meeting organizer’s Contact Card from the Meeting detail view.
Voice Mail screen
• Delete a voice mail message.
• Use quick options to return a call and navigate to the Contact Card from a Voice Mail message.
• Use Accessibility features.
• Use Speed Controls for faster and slower Voice Mail playback.
According to Microsoft KB3102247: “We are working to address this difference in feature sets and to update the capabilities of Skype for Business for iOS as quickly as possible“.
If you don’t really have problems with this limitations, here’s a good look of the client.