I'm just rewatching it at the moment, I missed whole chunks of it last night.
To be honest, I found the resolution with Moriarty a little disappointing, though the ringtone was hilarious.
I really like how the relationship between John and Sherlock has mellowed, with the easy banter of just knowing a person through living with them. John seems more in control of the relationship in a way, providing the voice of restraint between Sherlock and Mycroft, but also just seems more relaxed about the odd path his life has taken.
Mycroft: I'll be mother.
Sherlock: And there is a whole childhood in a nutshell.
I love the better look we get at the Mycroft-Sherlock dynamic, and their squabbling. Also, Mycroft definitely seems less polished this episode, losing his temper, etc. He's definitely lost that veneer of untouchable public school man of mystery. A lovely touch is his and John's telephone conversation after 'Irene' in the morgue.
But this episode is all about sex, and it's Mycroft who hints at Sherlock's avoidance and, dare we say it, ignorance of it. And it's lovely to watch him be intrigued by Irene. But also Irene's assertion that while John knows 'where to look', but Sherlock doesn't is really interesting.
...aaand I'm going to finish off watching the episode.