I missed this episode when it aired here in the US on PBS, so I downloaded the episode from iTunes. I think this is my favorite of the (three) episodes so far. The cliffhanger ending is pretty much begging the audience to push for more episodes, which they duly did.
Overall the series of challenges Moriarty sets Sherlock are engaging, and there is a balance between the mystery plot and the 'relationship' plot. I do wish they would throw Watson a few more moments to shine. In the first episode he got to be a man of action. In this one he mostly wandered around behind Sherlock with a bemused expression on his face.
The overall gay quotient (GQ) of Sherlock is similar to Torchwood or Dr. Who with fairly regular low-level references. In this case including Sherlock's basis for deducing that 'Jim' was gay and John's comment that it was good no one saw Sherlock tearing his clothes of in a deserted swimming pool building. (John: "People might talk. Sherlock: "People do little else.")