I have completely lost my level XI game and significant progress. I was very fair along in the PVP arena as well. I lost all of this dating back to October 28th when I attempted to restore my iCloud backup to my new iPad Air 2.
If Glu does not have any way to restore in this day and age of games, when everything from Simpsons to Angry Birds can restore, then I doubt I will ever invest time in their games again. I absolutely cannot bring myself to invest hours playing knowing that a warranty swap of my iPad would lose everything.