I don't have much complaints with regards to casting actually. I think it comes down to writing.
You make a good point about character development. There are some tv characters who are better than their book counterparts and there are book characters that are preferable over their tv counterparts. I feel quite gutted about how they have portrayed Catelyn Stark (especially this season; however I do love Michelle Fairley) because she was definitely better in the books.
I understand necessary changes need to be made for adaptation purposes but I'm not sure where the writers are taking the Daenerys storyline. I don't know whether its for want of having a strong female character but I don't know why they are willing to neglect the wrong elements in her story (same with Catelyn).
I also don't know why they have suddenly made Cersei quite frightened of Joffrey. In the books, she tolerated Joff's cruelty and would never dare hurt him. However, with that being said, I actually liked the scene in the throne room where Joff asks Cersei if Robert fathered bastards. It was due largely to Jack Gleeson's performance.
Joff is another big departure from the books because it was implied that he wasn't smart. But I guess if you have a kid as talented as Jack Gleeson, you'd probably want to sneak in a few things just so he'd have something more to do.
I had reservations about how Stannis Baratheon was portrayed but Episode 5 was closer to who Stannis is in the books and I was very happy about that.
I'll stop now. I've talked too much.
