I've re-read this recently, and while I count myself as a "follower" of the series in general (if for nothing else, because of the absolutely fascinating amount of fandom discussions it has generated), this wasn't actually all that good as a book.
All the weaknesses really stand out on a re-read. The flat worldbuilding laced with gratuitously bombastic exoticism - with the "mountain clans" and the Dothraki standing out in this regard - bugged me from the start, but I guess I kind of went with it as the plot went along. But once you're reading this kind of book a second time, the basic outlines of the plot are firmly implanted in your mind, and there's more scope to focus on what you're actually reading.
And... it's certainly not badly written. The story does draw you in, with its scope and constant voyeuristic potential for tragedy and destruction. But the devil, as they say, is in the details; and on this level, Game of Thrones kind of fails, for me at least.
The sexism and misogyny of the setting have been amply commented on by others; I don't necessarily have a problem with some worlds being darker than others, and I don't think that Martin is taking it "too far" in terms of realism. But again, the problem is voyeurism. (And in that respect, ASoIaF is a series that engages very much with the moral standards of its readers, very probably much more so than with those of its characters. Namely: why do [we] keep reading if [we] are as appalled by these elements as one would expect [us] to be?) In addition, the characterization flaws spring up sharp and heavy on a re-read - especially when it turns out that the author has concealed many of the "plot twists" with the crafty but ultimately low-handed technique of making certain characters' viewpoints unimaginably stupid, in the sense that their non-perceptiveness seems completely OOC (i.e, how were they even able to survive up to this point in their lives with all they've gone through?). In other words: the imperative is to (mis)lead the reader, at the cost of characterization. And there is so much "information overload" in the whole thing that it's just about possible to pull it off.
The quality of the writing itself also varies. Some sections are quite amazing - I'm quite partial to the descriptive passages in the prologue, as well as some of the pages of the final chapter - while others are... more difficult to shower with praise. Most similes read very artificial, and the language is modern enough that the few inserted archaisms (such as "must needs") have a very jarring effect. It is also rather tedious to read continuous descriptions of every new outfit every single semi-important character is wearing (especially "doublets slashed with X"). On a similar note, for all the "Point of View" philosophy supposedly upheld by the book, there is in fact very little differentiation in narrative voices. One would expect certain viewpoint characters to notice different things, or describe events in different ways than others; but it doesn't seem to be that way at all, at least not on the level of the language / writing itself.
All in all, I enjoyed it rather less than I remembered. For want of better fantasy reads to plow through, I've decided to re-read the first three books of ASoIaF; for GoT at least, I've had to revise my initial rating downwards. We'll see if the subsequent books leave a better second impression on me; they might well do, as I can't remember much from the details apart from the plot from my first read-through...