Skype for Business has rolled out across a good number of customers and it’s, generally-speaking, a great UI update compared to Lync. The clients’ histories were covered a few weeks ago, if you’re interested…
But there are a few differences that could catch people out. If you join a conference call, for example, it’s possible you won’t see the list of attendees, where with the old Lync client, you’d be able to quickly show them with a click of the chunky Participants button 
in the Lync meeting UI. In Skype for Business, during an IM chat or call, you’ll see there’s no equivalent participant button – there’
s the usual button to show the IM window, which shows the text chat section but not the participants button.
This has been moved to higher up in the UI – it varies depending on which kind of chat/meeting/conference you’re in. Click on the icon to the left of 
the text (hover and you’ll see the Open Participant List tooptip) and you’ll be able to view that list.
On a simple IM conversation, the same thing is true, too, only with a smaller button.
If you look in the Settings | Tools | Options page within the Skype for Business client, under the Skype Meetings setting, you can set the default on what happens when you join a meeting.
There are some other tweaks too, such as using the view icon on the top right of the meeting window – Galler
y View shows you a horizontally-arranged list of attendees’ mugshots, which can be right-clicked to interact with them. Speaker View hides 
all of that, but still shows a picture of you next to the person who’s currently speaking, and Content View hides both in favour of the presentation content that’s being shown (the “Stage”).
