Posted this in a different thread, but thought I'd post it in the sticky as well.
Personally, I'm finding it interesting reading the backstory of Ursa and how she came to be Fire Princess. I'm not sure if I like Zuko not being Ozai's son, but it solves an issue I've been having with the series. Have any of you realized that Azule (if Zuko really isn't Ozai's son) is technically a product of inbreeding? Avatar Roku married the sister of Fire Lord Sozin. Ursa is the granddaughter of Roku. To have her marry Fire Prince Ozai, the grandson of Fire Lord Sozin, leaves the potential for one messed up family.
To me, having Zuko not be a product of this explains why he wasn't crazy like Ozai and Azula. Although, I will agree that it takes away from the "inner tug of war" Iroh explained to Zuko.