FWIW it took about 30 minutes, give or take - wasn't watching carefully - for my iPad to backup to iCloud the evening of the 12th. My iPad has about 55GB of files but around 40GB is music and video. The total backed up was a little more than 4GB. Tried it again last night and it took about 10 minutes...but that would have been an incremental backup and not a lot had changed. So what I would expect would take a few minutes tops took a lot longer.