Jack found a way to bring back someone at Torchwood who had died. Well, sort of. [Not that Owen had been a zombie or anything like that, but he hadn't been quite normal, either.] He said there's nothing there when you die, just black. Not all that encouraging, I admit, but maybe it's different for vampires. I suppose we could ask him one day, although I'm not sure how coherent he is at the moment.