As for the episode, it was okay. I think expectations may have been too high for it. Mainly, laying the groundwork for the next seven episodes and, possibly, the 50th and Christmas specials. Also, I think Moffat might be spreading himself a little thin with Who, Sherlock, and the other stuff he has going on (is he still a part of the Tintin reworking?). Hopefully, he will clear his plate a bit and be more focused going forward.