IOS 8 Family Sharing on, but not showing shared purchases

No. Each family member would have to use purchases in the cloud to download your entire music library.

I know of several people that tried family sharing and I've gone back to one Apple ID because of how well iTunes match works for them. Losing that feature to gain the rest wasn't worth it in the short run.

My gut feeling is that sharing between two adults it's better to stick with one Apple ID and families with small children will prefer a family sharing in the 8.0 incarnation of the feature

Before Family Sharing, you could take someone else's iOS device and sign in to the app store with your account and download all/any apps you choose.

At that point, your password was needed to update, but signing out didn't delete the apps or in any other way prevent them from working. Let's set aside in-app purchases for the time being.

Family sharing changes this in that when someone joins the "family" - their Apple ID is used to download and update other family member apps. They do not show up in your purchases, they show up as the other named family member's purchase. All that changes is the password needed to install and update.

When you as a family member remove yourself from the plan - you get a warning that lists what will happen and basically, you immediately lose access to the purchases, photos, calendars and other items that were shared in the plan.

Rejoining the family would then let you re-download and re-sync the items.

You'll probably want to find a better way to use the family service than routinely joining and leaving or skip the family share and use the older method of signing in to multiple devices which doesn't immediately remove/revoke the items.