Theory about Doomsday:
The Daleks in the Void Ship were hiding in the void after the time war. The Genesis Ark is clearly a device for resurrecting, or recreating the Dalek race. I predict it is designed to convert the DNA of a species (humans in this case), perhaps with a good dose of raditation for starters, into Dalek creatures but the Doctor sets it to alter and kill the Cybermen instead. How the daleks are destroyed I can not guess, piece of Torchwood tech I suppose.
Shame to see the (a) Supreme Dalek killed again (the black one), hope it escapes 😛
Oh and how good was Army Of Ghosts! Best new series episode yet. Russell T Davies's vision of Doctor Who is finally fully paying off.