This is one of only two fantasy series i've ever read, and if the thematically appropriate sex scenes in this here are out of the norm of the genre, i'm glad for it.
There are very few scenes that can be described as 'erotic' in any of the books according to my recollection. Of course, I'm sure they are meant to be pleasurable to many of the characters involved, but from the perspective of the majority of the p.o.v. characters, it comes off as trivial and mundane. The aformentioned scene with the Lannister siblings in the church made perfect scence given that 1) they had not seen each other in some time and 2) they don't really believe in the sanctity of the church or really any other institution in a realm obviously more beholdent to the complimentary ideals of family and power than to any sense of a true public welfare/virtue or law; they are realists/cynics, as pretty much most of the major 'villians' in the series are. A crappier pulp author would have used a pretentious narrative to outline this and skip past the actual scene, but I think its a virtue that Martin shows as oppossed to tells.
As to the rape, he certainly doesn't endorse it, but nor does he judge it. Nor should he because the society he is depicting doesn't really do so. Again, show instead of tell and hope the readers get the subtext. I common place nature of rape is consistent with the themes of gender, class, and general status that are laced throughout the story and is IMO a much more important part of 'world building' than geography or a fantastical history because it gives the series texture.
By the way, I'm glad to see the next book is done. It's my favorite guilty pleasure read and I've already wish listed it on amazon.