Having been disappointed by the first episode, the pre-titles sequence set the tone for a much better, more enjoyable time. The moment Maestro played into the intro was just fantastic!
The story progressed at a good pace and Jinx Monsoon stole the scenes they were in akin to the way that Neil Patrick Harris did as the Toymaker. However the episode still lacked that little extra that turns a good episode into a great episode. The jeopardy was cranked up too quickly for a natural build and not played about with enough to actually believe it (even in the reality pause world of Dr Who). I suppose the musical number at the end fit but I just wasn't keen. Having said that, I'm sure plenty will disagree on that.
Notice I've not mentioned the Beatles yet, which was the big selling point of the episode? Well that's because their initial introduction was actually quite funny but they were pretty much rendered insignificant after that except at a very predictable point. I also felt the musical number could have sounded more Beatles-esque. Opportunity missed.
In summary, fun, enjoyable and watchable, just not great.