BUT there is of course things that could be done better. While one-to-one calls work well, I feel that on the group calls with many participants (say 5+) are not so good.
I think Microsoft is missing a huge opportunity when they are not taking Skype further and adopting some features from Slack and Google Hangouts. Most of the technology is there, they would just need to tweak it a bit to better match the requirements. Some things I would like to see: the concept of organization and associated rooms. Possibility to push messages to these rooms from outside systems (think CI and other notifications). For group calls I prefer the way Hangouts, GoTo meeting and WebEx works. Somebody sets up the meeting and then others join. The message history and search should be improved. With Slack you start relaying that you find the old stuff from there, in Skype the search is bad and the message history does not go very far.
Now that Microsoft also happens to have LinkedIn, they would be in pretty good position to create a communication solution that would span organizations.
I'm aware about Skype for business, but also a bit suspicious about how this will turn out. Lync feels more or traditional enterprise stuff that you run inside your own network and not something for the Internet.