I think the opening was intended to (SPOILER)reinforce how much of a dick Sherlock is, but also to help humanise him more too. Like, clearly he cares a smurfload about John -- gay jokes aside -- but Sherlock still doesn't get how normal people behave.
Mary is one of the coolest characters. She is so on the ball and clever in her own way, plus she is hilariously playing both the boys. And the way she just puts up with Sherlock and John going off on their stupid adventures, I mean geez she's too perfect. I think that's the reason she's gonna get screwed over -- not because she's new, but because she's too good to be true. The dynamic wouldn't work because it makes too much sense. Though I refuse to believe they'd pull a Mary's in danger plot immediately after the wedding episode, that'd be trout.
uhhh what else are my jumbled thoughts. Yeah I'm a bit annoyed at the lack of over arching thread in this season. Like, yeah, that one guy, but how is any of this connected? It's... not. And that's half the fun! Having things all tied together. Moriarty was such an amazing villain, I wish he was alive still ;_;
eh that'll do too many THOUGHTS UGH