I would just like to say what a nice feelings it finally ends, and who better then to finish off Aizen, Mr Sandal & Hat Man Urahara Kisuke, what a 110 years of grudge befall it finally comes to an end at least for now.But do not get me wrong Bleach does not end here, PERIOD.
Back to the question, to be honest, Mugetsu was so quick and I do not know what to say other than its too quick and dangerous it was like what Ichigo said "finish this in an instant", it was so quick. It was simply The darkness Ended too Quick. Then this happen, Ichigo notices Aizen who falls near him (and I thought finally Aizen a done deal but wait...) he was regenerating again, WHAT!!! And Ichigo started to lose his power like just what he and Tensa Zangetsu said, Aizen rose point his broken zanpakuto at Ichigo as Ichigo knelt down before Aizen, and still at that moment there is no conclusion, the outcome of the match I just thought it was a DRAW!!!
Then finally a spark pops out from Aizen chest and the man who Aizen owes the most appeared to give us what really happens to Aizen now and he was completely VANISHED and SEALED away by what Urahara said his new Kido techniques develop just for Aizen powered Hogyoku that he had instill before Aizen completely fused with the thing, and yes this thought came to mine had not Aizen become weak that Kido would not had worked and finally truly saved Ichigo in the end. There I said it as if Aizen was the winner in this final match up. Oh crap!!! For Ichigo sake, without Mugetsu that Kido would not work either!!!
That was my thought, interestingly what your thoughts are, base on what has happen in Deicide 23. Regards.