I expect that the series will have more viewers on this forum as it goes along, feel free to discuss what you think of the cast, episodes, and the changes from the novels in this thread.
Here's a cast list, it's pretty impressive.
Sean Bean as Eddard Stark
Julian Glover as Maester Pycelle
Charles Dance as Tywin Lannister
James Cosmo as Lord Commander Mormont
Peter Vaughn as Maester Aemon
Peter Dinklage as Tyrion Lannister
And so on..
The part of the cast that I'm currently skeptical about is Emilia Clarke as Daenerys. Her character will under go some changes for sure but I'm worried that she's present more as eye candy than anything else. Her abilities should be clear when things start heating up, ..and I don't mean sexually.
During episode 1 I had my doubts but with episode 2 now I think Lena Headey might just be right for her role as Cersei. I don't know if she'll be able to pull of Feast of Crows but that's a very long ways off. Currently, I'm just glad that her ability to manipulate and her deceptive skills are actually far better than I expected.