I've been having several problems trying to sync things. Before the update, I had added two songs to my library and after the update I tried to put them on my iPad but nothing worked. I managed to sync, again, but when I wanted to add more music, I experienced the same problem. And it has taken nearly half an hour for "Waiting for changes to be applied" to go away, if at all (I've gone out shopping multiple times and come back to a restarted sync at only 100 songs).
I've wiped the music off of my iPad twice and also reset all settings and I'm in the middle of adding all of the music back a 2nd time. I have +9000 songs in my library, but even then iTunes says it's syncing a completely wrong number (let's say I have 9000 songs, the sync says it's 8998), and I've had three alerts saying "We can't sync this song" in this attempt (happened to me twice in my first re-sync attempt). I didn't have any of these problems with iOS 6.1.3 or the previous stable version of iTunes. I am now sitting here for another day and a half to add everything back onto my iPad, with at least 5 songs mysteriously absent.
What am I to do if these songs won't sync if I unplug and reset and do everything again?
Also, I've noticed that "Group by Album Artist" will not work at all in iOS 7. It was previously working on my iPad, but all of the song orders were messed up if one song in the album was by another musician; e.g. if track 1 was by Queen, track 2 by Bon Jovi, and track 3 by Journey the order would be 2, 3, 1. The "reset all settings" fixed this but now it's "Group by Album Artist" feature isn't working. When I called Apple Care about this when it was affecting my iPhone they just said "Oh, it's a feature we may have taken out".