If download fails, you lose connection, or do something else using data while it's downloading It's completely erased And you must start all the way over. There is no reconnect or resume download option So make sure your data Speed and connection is Decent or you will be very disappointed. O and don't expect to transfer the files anywhere Unless you do the iCloud upload crap.. so if you don't plan to upload your download Make sure your file is Meant for your Idevice.