Aside from various book readers complaining about barking dogs or intact noses, the most frequent gripes I've read concern the incessantly graphic nature of both sex and violence in HBO's rendition of Game of Thrones. "Why did they have to stab her in the stomach? Over and over and over??" "Is it necessary to show whores playing with each other in the background of this-or-that scene?" "Did they HAVE to show him cut that horse in half?"
Did they have to? No, of course not. Should they? Abso-freakin-lutely.
GRRM has created a gritty, quasi-realistic world that harkens back to times in human history when death was an imminent shadow that stalked daily life. More than half your children were more likely to die before reaching the age of 10 than to survive long enough to lose children of their own. Disease, infection, famine, and the perils that accompany surviving off the land were just a few of the many futures you had to look forward to. Now let's throw in some war with a healthy lack of modern medicine, bake for four seasons (so far), et voila!
One of my biggest complaints with most of film and television is the casual nature grafted to death and violence, as though it is not horrific, like shooting paper targets at a range. There is no grit (or, indeed, gristle). Enemies are mere Storm Troopers ready to be mowed down to flaunt the prowess or slow the progress of this or that hero. We watch shells of ammunition scatter in slow motion while stuntmen flail in balletic arcs of defeat. This is more than sanitization; it is the removal of violence from violence, which makes violence more acceptable, normalized, banal.
But violence is not casual, nor is it convenient. It is messy and traumatic and shocking, or at least it should be. And this is one of the many things Game of Thrones has done absolutely right--to linger too long, to make the audience uncomfortable with it, to shove its brutality front and center on the screen. Did they have to show Talissa stabbed repeatedly in her pregnant belly to pull off the Red Wedding? No, but the writers and producers and director decided to take an act of butchery and show it for what it was, and for this we should be grateful. If it makes you uncomfortable, good. It's supposed to. Violence should not be easy to watch.
We are also wont to impose our modern, Western devotion to the individual upon this world, wherein every life is sacred and all individuals have the right to the best possible futures and outcomes we, as a society, are meant to preserve. To expect this in our world is naive; to expect it in Martin's world misses the point entirely. The smallfolk are not even allowed their own family names, which should speak plenty as to their inherent value. Women are considered property to be bought, sold, and traded for the best advantage, and once exchanged belong to the receiving household.
Regarding the nudity and sex itself, I do not see any of it as gratuitous . Even when it has been used as a pretext for exposition, we have learned something about the characters involved. We also learn a lot about the value of women in this world, which paints a great contrast for the women who are not relegated to "whore" status and what they must fight against. Sex is often the fulfillment of bodily functions but also used to bend power in different directions, as we have seen with Jon Snow & Ygritte, Cercei & Jamie/Lancel, Littlefinger & Everyone Else, etc.
As Cercei has said, sex is a weapon, and it can often lead to someone's downfall as sure as the point of a sword (RIP: The King in the North!). The sex in this series, much like the sword, tells a story, and that is what fiction, when done right, does so well: it shows us the truths that truth doesn't always show us. Facts are information. Stories are meaning. One of the meanings GoT gives us is that life is a brutal and bloody business. Our lives have meaning because of their delicacy, because they end, because we are constantly aware of our finitude, and nowhere is this more clear than in this gleefully graphic series.