Failing to restore my iPhone 4S from iCloud backup over wifi
I had the same problem. Tried for days to get it to work. On my 17th try, the restore completed. On that try, I was keeping the display active by tapping it every 40 seconds for around 2 hours and I had also turned off all encryption on my router. Not sure what caused it to work this time.

The weird thing is, the restore finished when the status bar said there were "about 3 hours" left in the restore. Seems like it miscalculated the size of my backup or something like that.

Apple really needs to figure this out.