While I thought Mycroft's apparent mind control of the whole family one of the most far-fetched things in the episode, I was able to buy into it and I found it an interesting concept.  How do you think he would have been able to do that? You would think that parents would be aware of a lot of stuff, would have heard from Victor Trevor's parents that their son died.  But perhaps if they forgot they would not have remembered the connection to their daughter?  

I think it makes sense for Mycroft's character to have been so determined to do this that he was able to change his parents' memories, too, since he's been determined to do things (even if it's not necessarily welcomed by other characters, like Mrs. Hudson or Sherlock) at other moments in the series.  He seemed to have determinedly wanted to change what everyone's memories are: Sherlock's and his parents.

Still, I was kind of sad that Redbeard turned out not to be a dog after all.  I still thought it was a very interesting twist, though, that Redbeard was a figment of the imagination and a replacement for a character.  I don't think it's impossible, since people often mask their trauma as something else in their mind, or suppress it, in some cases - even if, no doubt, exaggerated for dramatic effect.  It was so sad that Sherlock's first friend was taken away from him.  I never would have expected them to incorporate Victor Trevor in that way, if at all, but since they've focused only on Sherlock's adult life and childhood, I think that putting Victor in Sherlock's childhood worked with that, fitting him into parts of the story that had been discussed before.

As I was writing the above bit (which I have been thinking about since Sunday night), I remembered Mycrof saying "Caring is not an advantage."  I think that is given another dimension now.  Not only does Mycroft distance himself from feelings, but he also tried to keep his family from caring about those past moments as they really happened, because he did not want them to be harmed by them, because that would not have any "advantage" for them. It would seem that that has to do with the reasoning behind his decision, anyway.

Does anyone else have more thoughts on this?