I thought it was an interesting move to have Sansa reveal herself. It makes me wonder what the future holds for Sansa and Petyr. Sansa is definitely looking out for Sansa, but I wonder if Petyr is foolish enough to think that Sansa is into him. She did kiss him back, and she did lie at the inquest to protect him...but like I said, Sansa is looking out for Sansa and both of those things ensure her own protection. But Sansa does hold romantic notions about chivalry, and does seem to acknowledge that Petyr did a lot of things to protect her, so who knows how that will affect her perception of him. I'm looking forward to see how this plays out next season.
I have to add that the whole trial of the minstrel and general Alayne subterfuge could have eaten up half a season.