I see this episode as an episode of changes. For one, the mood and pace of the first episode changes in this one. For another, the entire show changes. Now, there is more action, a faster pace, and huge, world-changing (so to speak) twists. It is a continuation of the last episode, but it is also a whole new episode of its own.
What this episode does is flow. It manages to tie together the events left over by the first part with even more ingredients, creating an explosive mixture; Hakoda, Suki, and Chit Sang, the failed escape, and Azula, Ty Lee, and Mai reappearing. It's stuffing even more characters with their individual agendas into a tiny, confined space, and letting it all play out. And all the while, the plot and the events move along swiftly and smoothly, adding more and more complexity as the episode continues.
Indeed, this is a very multi-faceted episode; the writers had to come up with a second escape plan, they involved Azula, Ty Lee, and Mai, Mai's reaction to Zuko leaving the Fire Nation are finally revealed, and then there's the whole gondola scene that is the high point of this entire episode. In fact, the new escape plan fits the overall feel of this episode, where there is a lot of messy action going on, just like how the last escape plan fitted the first episode's feel.
This scene deserves special mention, and not only because it contains in itself an arc of tension, going through all the phases of introduction, build-up, climax, and resolution. Our heroes seem to have made good their escape, even though we know that something bad has to happen. Then we get the heroes confronting their arch enemies, the wire being cut, and then finally Mai's rescue. This scene would be very good just up to there, along with some wonderfully animated combat, but it's the ending of this whole ordeal that had my head explode.
The scene is very well written, with good dialog, and some excellent cinematography. Mai has already betrayed Azula, and though that is a very big issue, Ty Lee's sudden intervention by joining Mai's side is another blow in the viewer's face. To be honest, in order for the story and the characters to work, this event was more or less inevitable, but seeing it happen is still a huge surprise, partly simply because it was written and performed very well.
While the plot is certainly the best and most striking part of this episode, the music is also worth mentioning. The Boiling Rock theme returns once again, even though not as extensively as in the first part. Along with that, the animations and cinematography are excellent, such as during Suki's awesome acrobatics scene.
All in all, this is a very great episode. It has lots of action after a more quiet first part, it changes many of the big issues of the show, and the presentation of it all is in a very high quality to boot. There is only one gripe, the one thing that prevents this episode from attaining a higher grade: The ending. The ending is very sweet, and Sokka, Katara, and Hakoda get reunited, but somehow, the whole feel is off, and the culprit is mainly the dialog. Sokka's line seems a bit ridiculous, and so do Chit Sang's introduction to the group, and Toph's final question about meat. The two messages - a heartfelt reunion and funny lines - don't mix at all, and ultimately cost this absolutely fantastic episode a top grade.