Good point about the reapers, given the line in Father's Day about 'there's a man alive in the world who wasn't before,' and that's basically what set the whole mess going.

I suspect the next story will draw on the idea of the Doctor's interfering having knock-on effects. There was a line cut from Last of the Time Lords where the Master tells the Doctor that he allowed all this to happen. By ousting Harriet Jones, he left a gap that shouldn't have been there, one the Master could exploit.

But seriously, Cheshire Ood? WTF?!