Apple Push Notification reliablity
The notifications come through 99.9%, I think the 0.01% is when your phone doesn't have network. That is the only reason it won't go through, unless you have a poor server with 10000 requests per second then yes that will fail. 

So for best results just get a good server. I don't think you can help people with cellular coverage. Even if you did run in background they won't be able to pull data from internet if they don't have cellular network. 

Apple just wants you to not rely on it 100%, so make a backup plan for it, let the user know the app can't connect to the server if there's no network. I'll say do push notifications, then if that fails try get from server manually and make local notifications, if the app can't make connection to the server fire up a local notification that says it couldn't connect to your server.

Hope this helps?