Thanks for this thread. I bought a used 2010 Prius (20,000 miles) and just signed it up. I learned that at about 11,000 miles, apparently the previous owners filled with 85% ethanol instead of regular 10% unleaded. I sure hope that doesn't void the warranty down the road.
I registered too. I think this is great for having all your records and reminders. And in future, will tell you of any other potential fixes (minor recalls/updates ) to be performed.