I loved nearly everything about this episode, most of all Peter Capaldi's Doctor. He was wonderful, absolutely awesome. Hilarious, dark, clever, and heartbreaking in proper measure. I also loved the new opening titles and theme (especially since I loathed the previous version of the music so much). Very, very cool.
Clara does seem to be getting some fleshing out as an actual character, which is good. Hope to see more of that.
Wasn't super excited to see Vastra, Jenny, and Strax again, since as others have said they tend to be used mainly as "funny" caricatures, but they were all right this time.
Other than, yes, a few too many moments of harping on how "old" Twelve looks compared to Eleven, my only real objection (or possible objection if it turns out how it looks like it's going to) to the ep was the final scene. I agree with this entirely:
I would really like a different arc this season. If possible. Ahem.
Was that really Elisabeth Sladen's husband as the homeless man? Aw geez. *sniffle*
I think I need to watch it again, to catch all of the Doctor's one-liners that I missed because of lack of subtitles, Scottish accent, and rapid delivery. Oh, and I must chime in and say I loved the Doctor's scene where he asks Clara to try to see him. Beautiful - almost brought me to tears, more than Eleven's phone call.