I used to sync all music from my Mac to my iPhone locally, but decided to turn on the iCloud Music Library switch today after getting Apple Music and realising that the switch has to be on for Apple Music songs to get synced across to the phone.
When I play a song on my phone that's stored locally, it decides to delete it and then stream it. If I try to make it available offline, the song downloads and then I assume it's saved locally again. When I try to play it again, it does the same thing - deletes it and streams it instead.
I hope this is just a temporary bug... anyone else having this problem?