Actually the theme arrangement was definitely changed along with the visuals. I'm not sure how I feel about the theme right now; I'll have to listen to it properly once I'm back home. The new title sequence is a nice change, though not particularly amazing. Smith's face is hardly there at all (blink and you miss him), but overall the whole new look is a nice change, including the TARDIS doors opening on the post-credits scene.As for the theme song, I was a little disappointed it was the same theme as the previous two seasons but the visuals just changed. I loved the visual change, but I really wish the actual theme was a little more simplistic (Like during the RTD era) than what we've gotten.
Loved Jenna-Louise (would have preferred Victorian Clara to be the companion), loved seeing Vastra & Jenny again (spin-off please!), and Strax was surprisingly amusing. The snowman plot was a little tame compared to all the good stuff (oh, including the new interior!), but overall a very enjoyable special.
Bring on 7-B! (SPACE here didn't show a preview clip of the rest of the season, so I guess I'll have to catch that on YouTube)