Dany was always my second favorite character, right after Tyrion. And I did not mind her becoming the Mad Queen...I was bothered about how they showed her becoming the Mad Queen. Dany had always been willing to do what she needed to do to achieve her goals. She could be cruel given the right set of circumstances. But what she did not really do was harm those she saw as innocents.
Now, I think there is an argument to be made she could view every citizen in King's Landing, bad place maybe even Westeros, as being complicit in the evil in the world. But I do not think that argument got made. Instead, she just seemed to snap. And that seemed very much out of character for her, something that needed to happen for the purpose of getting the show done in six episodes rather than a natural development that made sense.
Of course, milage varies.