Personally,
As far as the Satsuki part of the arc goes, or the first portion, I've been pretty much fine with the whole Satsuki subplot... I actually liked how it turned out. But, that is dependent on the assumption she goes back with him at least and is not dropped from the story. The reasoning being is if she is dropped somehow after this arc, then the entire arc to me would make little sense except as a distraction from the main plot with Caster and the detective and everything looming ahead. It would also have wasted all the development given to her character and growth into her powers...
As far as the Caren part of the arc goes, I know little outside the respective anime continuities (FSN/Tsukihime) though, and am not really all that into this Caren and cursed museum sword subplot.
I cannot imagine Caster being happy about Caren and Ciel playing him like they did either...