WARNING: iCloud Music Library just destroyed my Mac's iTunes Library
I have a 13000 song library on my iMac. Installed iOS 8.4 on my iPhone this morning and had Apple Music and iCloud Music Library going...Everything was working fine on the device. Got home and installed 10.10.4 and iTunes 12.2 on my iMac. It asked to turn on iCloud Music Library and I accepted. All of the sudden it starts overwriting my album art with completely wrong art (example: Weezer showed art for a Radiohead album) on both my iMac AND my iPhone, screwing up metadata by putting random songs in albums where they didn't belong (there was a Cursive album where the first track was listed as a Foo Fighters song). Even worse, when I'd click to listen to certain songs, it would play the wrong song/artist, like the metadata was hijacked. What in the ****? I've had this library organized perfectly for the better part of a decade and Apple Music screwed it up in minutes.
I was able to restore everything through a Time Machine backup and made sure NOT to turn on iCloud Music Library when I re-opened the .itl file. What a disaster. Hopefully someone from Apple reads this. Thinking it may have something to do with a iTunes Match account I had briefly a few years back. But yikes, can't believe how much damage it did in 5 minutes.