Hmmm, the vaizard are surprisingly well informed. An ally in soul society? One of them with some sort of visions or spying power or something? Although I suppose they could have met Aizen in the past. Maybe they are his old experiments? Or maybe their existence and powers are what led him to experiment in combining hollow and shinigami powers?
And Ichigo vs his hollow self is always welcome. I hope that the hollow version of Ichigo isn't completely destroyed by this... he's an amusing character. And I like the setting of Ichigo's inner world. One of the more creative parts of the series.