Smart Albums - iCloud photo library
It is truly disappointing and shortsighted of Apple that Smart Albums don't sync to iCloud Photo Library. This makes absolutely no sense at all!
We had dozens of smart albums in iPhoto for OS X, and then we converted the entire photo library to Photos. Then we turned on iCloud Photo Library to sync our photos to all of our devices.
Yet lo and behold, our smart albums DON'T SHOW UP ON OUR iOS DEVICES. This is a gigantic step backwards. All of these smart albums USED TO SHOW UP ON OUR iOS DEVICES when we synced via iTunes, but Apple has now removed this capability from us by introducing iCloud Photo Library!
Way to go, Apple. Good way to take another step backwards for your customers.