A host of improvements. The people hub update is a refreshing sight. In previous builds I would link contact accounts only to see them unlinked later on. Now not only do they stay linked, but the hub displays multiple accounts displaying the latest information they posted. In addition if you swipe left, just like in previous Windows phone OS's, it links you to their facebook page as well. I like the skype messaging integration, but don't understand the difference between skype video in the app, and the skype video app itself. My outlook now syncs with my calendar. The phone seems to process information faster. I'm having issues with 6Tag not opening up, which is kind of an inconvenience because the official instagram app doesn't allow you to upload videos, and I'm having issues using the video upload apps for instagram. I can definitely see the cross connection with my surface 3 and this is how I think MSFT will sell the windows mobile concept in the future. Not as a stand alone phone, but as an extension of you Windows 10 experience. All in all, I've been using it as my daily driver on the 640XL and haven't experienced to many issues.