Well, yeah, there is a bit of Who somewhere in there :-) Not too much of it though.

If I remember the books correctly (I did read all the stories at some point!) no there isn't a lot of character development of Holmes and Watson - it's all about the mystery and how Holmes brilliantly deducts the truth. Watson is sometimes comic relief and sometimes saves the day. I also never thought about slashing Holmes and Watson from the books - that only started with Guy Ritchie's Holmes for me, and it certainly will continue with Moffat's!!!

I suspect there is an arc in there as well which would explain the strange ending.

But yes very enjoyable indeed!