I’ve never before recommended that you don’t upgrade to the latest version of iTunes, but I am doing so now. If you haven’t yet done so, don’t upgrade to iTunes 12.2, at least if your music library and its tags are important to you.
I installed iTunes 12.2 on my test computer, a MacBook Pro, and quickly found that it changed a lot of my artwork and tags. This is a small library, containing music copied from my larger library, which is on my iMac. So I’m not particularly concerned about the integrity of the tags. I use that library for testing.
But it is a mess. I have an iTunes Match subscription, and many of my tracks show as Apple Music files, which include DRM.
There is a long thread on Apple’s support forums, with people discussing this issue.
The real problem is the iCloud Music Library; that’s what gets tags and artwork from Apple’s servers, and replaces yours. If this option is off, then nothing will be changed, but it may be on by default when you launch iTunes the first time (this depends on whether or not you’re logged into the iTunes Store).
I had high hopes for Apple Music, in part because of the unique ability Apple has to integrate both music you own and music you rent; combining your own iTunes library with what you can stream. But it is a dismal failure.
My music library is sacred. I’ve spent a lot of time ripping CDs, tagging files, and adding artwork. One poorly designed version of iTunes can ruin all that work. If your music library is important, don’t upgrade to iTunes 12.2.