I have an app that uses Core Data with iCloud sync. It works great in iOS 7.
I'm having some trouble since running it in XCode 6 though, even on an iOS 7 device. Here's my test:
- on iOS 7 device: Download current live app from app store
- Sync data from iCloud
- Build and run new version of app
- Persistent Stores change, original data no longer available
Here's screen shots of my provisioning profile and xcode setup:

I've also tried the following entitlements:
- Just
com.apple.developer.icloud-container-identifiers com.apple.developer.ubiquity-container-identifiersthis is what I had before. When I run the test with this in place the data is there first time but not on second run. There's no events about the store changing, but it saysUsing local storage: 1on first and second run- Both of the above. Get the same results as #2