As I wrote before I use Skype extensively. And usually I talk few with few people at the same time. In old Skype it was possible to open separate conversation window for each person. Not only it saves time to switch between different conversation, but it also allows to check who is writing and depending on priority answer now or later. Without this feature it is suitable for occasional use like few messages per day with one or two people. If you are chatting with 5-10 people, 50-100 messages per day it was not that usable. This was biggest feature I missed in new Skype.

And finally, Microsoft added this feature back. In fact, they added it some time ago.