Small tweaks to the “Photos” app.
For me, the fact that the “Photos” app has some seemingly minor—but noticeable—kinks worked out has been great. Most notably, now you can swipe across a grid of images to select multiple images instead of having to select each image one by one.
Also, there is now a “Screenshots” album which seems to be a “smart” album that only shows up when you take a screenshot. But unlike other albums where deleting an image in an album only removes it from the album, the “Screenshots” lets you delete screenshots completely from your device.
This is a quite nice way of dividing up content that makes it easier to manage screenshots when mixed in the context of “normal” photos.
And past that the order of images when viewing via “Photos” or via “Albums” is now exactly the same.
Prior to iOS 9, if you viewed photos in the “Albums” view it would be oldest to newest from left to right, but in “Photos” it would oddly be newest to oldest from left to right.
Now with iOS 9, both “Photos” and “Albums” show oldest to newest from left to right.