I did think poor Bill was set up to be nothing but a sacrificial victim to Moffat's love of angst. The wet gf was a plot device to undo everything again and turned from dangerous (and the doctor all protective about it) to all lovey dovey and helpful. She would have been a useful ally to have in the earilier stories and is a bit deus ex machina turning back up like that all,of a sudden. Being Moffat it's almost deus ex Mycroft actually :-) I also notice that Bill, like Clara, got a exit with a powerful alien friend and an elbow in (or is it out?) to carry on exploring time and space. Moffat has created a lot of loose characters left to fly around untethered.