There have been bugs persistent in iOS since at least iOS 8, maybe 7. Most of them that affect me have to do with the music app and iBooks backups.... my purchased books are backed up as if they are downloaded PDF's. In iOS 6 and prior, iCloud backup would mark the book as being on your device and sync bookmarks, but wouldn't actually back the book itself up, as it lived on Apple's servers.
Music syncing never works accurately for me. In older versions, syncing was near-flawless. Now, I end up with duplicate playlists that always need cleaned up when I edit playlists on my device, sometimes my tags don't show up correctly (songs display on iPhone with the Grouping name even though on iTunes, all files are tagged correctly).
It's still the best by far for me, and I love Apple Music, but I'm not putting my music library in the cloud since iTunes Match hosed my library years back. I prefer a local library and selectively downloading what I need. The idea of having a cloud-based iTunes library is great, but it hasn't worked for me, I rely too much on smart playlists and nested playlists.
The TV app is great for searching and content discovery, but its dog-slow if you just want to load up a local video. The whole point of storing things locally is for fast and easy access to it.
Overall, minor quibbles, but the iBooks issue is one I pointed out whenever I first discovered it and it still has not been fixed. My health data backup was huge once as well, haven't checked if that's been fixed or not.
*As for the actual question of the thread, it's a great phone. Gestures are becoming second-nature already and I enjoy a plus-Esque sized screen in a smaller form.
