I have just finished reading Part 3 of the Promise today. =D And man, it was great. Argh...But now, I can't wait for the Search trilogy to start, especially considering it deals with Zuko's mother mystery finally.
I liked The Promise too, although I personally felt Part 3 was slightly weaker than the other chapters. In part because it seemed to be trying to cram too much in, and as a result it swung wildly from drama to humor and back again. Still, I can't wait for The Search either.