SPOILERS (as in: Gil, don't read if you haven't watched Season 7
)
1.) The "Villain" of the episode was actually known as the "Great Intelligence". For anyone that does not know what that is go to
http://tardis.wikia.com/wiki/Great_Intelligence
So Moff made a callback of an Great Old One, something unexpected and if it was not for the dull as hell story could have been far more interesting.
Interesting, and I read that House (from Neil Gaiman's episode) was supposed to be GI as well. I wonder why they didn't expand on that plotpoint in the Christmas Special then, knowing GI and the Doctor have a history.
2.) The Doctor's acquaintances in the episode would have been far better companions than Clara. Their role in the story to no matter the purpose served a far more interesting interaction than what Clara would have had. Plus a Sontaran, a lizard, and a girl in a TARDIS having adventures just sounds straight up fun.
I actually would like to see more of those characters, but I doubt Moffat will let that happen...
4.) Sherlock Homes Reference = Doctor Who. Considering that its no secret that Moff writes for "Sherlock" (and actually gives a damn when writing as well!) This could just be a reference just to stir up fans of both series to go nuts about it on the internet. I already saw it first hand.
I thought of that too, his thinking: "I'll be lazy and combine both!"
6.) We could have had a change in direction and have something similar to the First Doctor again. Not wanting to interfere with humanity, not dealing with/caring about annoying companions, not being afraid to kill if needed. A Doctor that just did not care for playing it safe and responsible anymore just someone who has had enough of the way things are and will only do things on his and ONLY his terms. Sadly with Clara it seems he has once again softened up and will become a pushover for said companion. Give me my goddamn GRIMDARK Doctor already..
Yeah, it was such a quick turn-around, it's like Matt Smith can only be serious for two seconds before being loving and caring again. I really had hope that we'd see a bit of Eccleston in Matt Smith now, but I doubt it. If Moffat makes him "grimdark" later in the Season...I guess it wouldn't be all that bad, even though it'd be too late.