Move to folders!
I lost ability to be able to move emails into folders ! Now the quick actions swipe right le left let's me choose only to: mark as read or unread, delete, archive, pin, flag or nothing. I loved that I used to be able to swipe and a bar of options 3 or 4 appeared (which I could customize to the actions that I personally tended to use more) and then CHOOSE from my swipe different actions - one of them being, and one that I absolutely loved, the ability to move to folders. I'm BIG on that as its how I operate. Anything that stays in my inbox is things for me to act on. I absolutely loved that capability.
Still using app because of the Calendar function and synchronicity with Outlook (color-coding for categories and ability to manage other people's calendars that I have the rights to -> that is still my quintessential purpose.) but could REALLY use some updates and fixes.
I'm using iPhone 6S+ and running iOS 9.2.1 and OWA version 15.01.036100 with all notifications allowed via iPhone settings Notification Center (badges sounds and banners) as well as allowed access to contacts, photos, background app refresh & cellular data.