Most locations throughout USF, IOA, and the onsite hotels accept them. You do indeed need to tell the TM at check-in that you would like to add charging privileges to your room key and set a limit (if you want). At CityWalk, most locations also accept them but it requires a bit more work. Sometimes they have to phone the hotel, so I find it easier to use a credit or debit card or cash at CityWalk.