Having used the Betas of both iOS 9 and El Capitan, I can tell you I see bugs in the release version of iOS 9 that have been reported and remained for some time.
Some Podcasts that are available download then disappear.
Syncing via Lightning-USB of iTunes content comes up with some distinctly funky results.
The data available on m iPad Air2 shows differently on different screens within iOS and another completely different number on iTunes on My Mac. There was no problem with sync on the most recent Beta.
Apple, please take the burden of all media off of iTunes in favor of something that works properly- and no the answer is not over the air cloud sync.