After spending hours on trying to sync my music library and my movies. Trying all the various suggestions in these threads with somewhat limited success, de-authorizing my previous phone did the trick - for now. Who knows the next time I try and sync?!
I have an iPhone 6 Plus with 64 GB and running iOS 8.0.2. First nothing worked with syncing my music and movies. Then after restoring my phone, removing everything on it, not syncing through iCloud, it appeared that all my music synced up - not the movies. But when I tried to play back the songs on my iPhone only those that I purchased through iTunes would play. Those that I imported in from my CD collection over the years - appeared as if they were there, but when I clicked on them they greyed out and it would skip ahead through all the songs until it found an iTune purchased song. Weird! So it appeared that only iTune purchased songs synced over correctly and would play. Same for movies. Those that were burned and imported from my DVD collection would not sync over to the phone.
Now that I de-authorized my previous phone - everything synced over, music and movies, and all appear to be accessible/playable now.
I must say this is the worse experience I have ever had with Apple products and software. My last phone (4S) several years back - plugged it in, synced it up - perfect first time and every time thereafter. This has got to be a bug with iOS 8 and the new iPhones. Based on everything I've read on several forums and news reports this is not a small portion of the 10 million new iPhone 6 & 6+ users. Apple is not instilling confidence lately. From their streaming problems when they announced the new iPhone 6's to this. I'm so excited by the new Apple Pay coming soon - but my excitement is one of extreme caution now. What bugs will there be with that and will my credit card statements show double billing or worse??? A BIG vote of "no confidence" right now. Apple has to solve these problems and ensure it's customers that it will do better in the future - and demonstrate it!