Don't get me wrong, I'm not disappointed that the Master showed up, I'm disappointed that *that* was the Master. He's my favourite of the Doctor's nemeses, and yet they've managed to make me hate his appearances in the new Who. And while the Rani may have paled in comparison to the Master, at least she was an established female villain.
And the Master's ingenious plan is to create an army of Cybermen using dead people whose personas are housed in a Cyberman Matrix? Because... yeah, I just don't see an explanation happening in part two that makes it palatable. And since they got unleashed on the city/world I sense yet another wave of the magical status quo wand as our resolution.
As far as Capaldi's Doctor goes, I really like him. Character-wise he reminds me the most of classic Who. If his stories were two or three parters and paced more like classic mysteries it'd be grand. I imagine they've lost the attention of the swooning young women, though.