It's definitely a book of two halves. The first part was a bit too long. The second did make up for it in my eyes, tho. Also, I really liked how Granny didn't share Esk's belief that women could be wizards but still went on to support her endeavours - even to the point of fighting Cutangle.
I agree, but I would have liked to have seen more of Esk trying to combine the best of both: Witchery and Wizardry, to create something new that's more about being herself than trying to fit somewhere else. Although I guess it could be argued that perhaps she and Simon did just that at the end?
I see what you mean. Yes, I hadn't seen it from that angle, but mostly because of her being nine. If she had been a teen that would have irked me, too. I mean Magrat is basically an older Esk.
I'd be ok with a novella; they don't all have to be full length, and this one would have been better as a short story/novella. Either that or cut out most of the middle bit and expand on the ending post-battle a bit more. Everything after that battle felt too rushed.
I love Granny, but I get where you're coming from. And agree that this one was more uneven than the other Discworld books. It picks up again with Wyrd Sisters.