Skype is frankly a disaster. Not only the personal app, also the Skype for Business app. Chatting works, but don't try to use any other functionality, since it breaks so easily.

But first (with great distance) on the list of failed Microsoft products is their accounts. Ever tried to login into msdn? Even our sysadmin who's is daily job is to get this right fails many times. The UX is so confusing and ambiguous, it's not funny. Everytime I need to deal with it I am seriously considering moving away from the whole MS ecosystem.