To be more accepting of people who are different, especially those who are socially different.
Through this forum, which let's face it wouldn't exist we're it not for Sherlock, that people from many different cultures and countries can have a lot in common, more than we might initially think.
That persistence often pays off.
Not actually a complete revelation this but that we should all be wary of being manipulated by the press.
Again not a complete revelation but how quickly the public can turn (or be turned) from idolising someone to vilifying them.
That knowledge is never wasted. W may think that something is a waste of time (yes Sherlock, like the Solar System) but you can never be sure when it will come in useful.
That true friends are very, very important and that quality and not quantity of friends is the key.
'Honesty': this is dealt with in two very different ways in the series. Sherlock can be completely dishonest when it suits him (such as pretending to be an old friend of someone who has disappeared, turning on the tears and wobbly voice, just to get information) but can also be so bluntly honest in a social situation that it is positively cringing (e.g. Jim being gay or Xmas in the flat). Basically he does what suits him. John, on the other hand reminds me a bit of Jimminy Cricket in Pinocchio (not that Sherlock equates to Pinocchio because the puppet lied continually). He gives Sherlock all the social cues he is missing. He understands the value of 'white lies' whereas Sherlock is, frankly, clueless. Sherlock would want someone to tell him the blunt truth and not namby-pamby (love that word) around afraid of hurting his 'feelings'. So although Sherlock 'cries' and does the wobbly voice at the end of Reichenbach Fall, he also lies to John, massively as it happens, so this actually fits in with his normal behaviour.

---------------------------------------------------------------------------------------------------------------------------------------------
Don't make people into heroes John. Heroes don't exist and if they did I wouldn't be one of them.
