Microsoft’s Universal applications -- Mail, Calendar, People, Photos, OneNote, Groove Music, Movies & TV, the News, Money, Weather, and several others -- run a gamut from reasonably usable to truly pathetic. Let me start by looking at one of the good ones: the new Universal Mail app.
Universal Mail has many of the capabilities you would expect in a modern email program, though it won’t consolidate inboxes, and it always shows threads in conversation view -- you can’t simply look at mail as it comes in, chronologically.
The Calendar app works well, particularly when fed a Google Calendar. I was quite startled by how well changes in the Windows Universal Calendar app showed up on my Android phone.
But the People app is a cruel joke. If you can figure out the interface (click the ellipses icon on the right edge of the left pane, choose Settings), it’s possible to add contacts from Outlook.com, Exchange, Google, iCloud, and POP or IMAP. If you choose to Get Social Apps, you see a rude notice from the Store that “Your search for '' had no results.” The People list does little more than an Outlook 97 Contact list -- less, in fact, because you can’t export it.