My second, third, and now fourth re-read however, have really changed how I see Cat's character. She is despicable beyond measure. I literally cringe when I read any content that involves her speaking - to anyone - about anything. However, without her, and some of her ridiculous interludes, some of the better story lines could not have come to fruition. Especially Jamie. The story needs Jaime. Once Robb captured him, he was stuck in a cell with no way out, but Robb needed that victory in the Whispering Wood, so that's how Martin gave it to him. Since there was no escaping the cell, it was only logical to send the grieving mother in to set him loose.
Initially, UnCat was such a striking prospect. I had envisioned something entirely different than what we've seen though, and quite honestly, I don't see the relevance of requiring that Stoneheart actually be Cat resurrected. Could it not have been another character. Someone we have not met yet? I know ADWD will yield no answers, but mayhaps we'll know why he chose her later on. I'm just done with her though. She is by far the weakest structural character in the story. Lower than Lord Frey... that's pretty low.