Broken for me. I added the app to my iPad and then upgraded to LR 5.4 on my PC and started to sync a few photos via Collections and I keep getting the message:
"Sync has been turned off. This appears to be a backup catalog which may be out of date with Lightroom mobile."
To make this your sync catalog, go to: Edit > Preferences > Lightroom Mobile and click the "Delete All Data" button to start fresh.
I have done this numerous times and am getting nowhere. A tad buggy out of the blocks, me thinks!