I've been lurking on this thread, finding all the discussion fascinating. I do agree that with today's near-instant access to information, historical authors are under more pressure to ensure accuracy. However, I believe that historical fiction is not intended to replace or even enhance nonfiction history. Novels are by their very nature speculative; we re-invent the past to make sense of our present and, as such, bring our own perspectives to it. Some authors stray more than others, but in the end when I pick up an historical novel I seek to be entertained, first and foremost. Glaring inaccuracies do affect me, but by and large I tend to be forgiving if the story is dynamic enough and the characters engage my imagination. I grew up loving historical novels that today would be considered wildly divergent from our current exacting standards; these inspired me to seek beyond facts for the emotion of the past, both via other novels and in nonfiction.
On the subject of author notes, I have to say that these are very encouraged by editors today. I didn't have one for
The Last Queen; my editor requested that I compose one. I've also read on forums, this one included, that readers appreciate those author notes addressing what has been fictionalized, speculated, etc. In order to write a novel of say, a true-life person, we often have to adjust time frames, condense events, leaving out some things to enhance others. I believe readers are entitled to know the most important areas where we do this, as well as understand some of the thought processes and research that went into our particular fictional accessment of a character or event. I never claim to be an expert, because I am not. I'm a writer with a history degree and I choose to write about historical characters through the prism of fiction. That said, I do not regard my books as "Historical entertainments" - though, you could argue, my Tudor spy series fits this bill - simply because I don't feel I take my particular speculative inclinations to an extreme, but neither would I claim that my novels are as factual as nonfictional accounts (where, by the way, I've found errors too, on occasion.)
Not only do many readers have less time and patience to wade through a thoroughly unadulterated interpretation of an historical life, but such books can also become rather long and the majority of editors require absolute word counts for this purpose. I cannot emphasize this enough. Word counts, which are directly related to print costs, and a book's ultimate retail price, are key in publishing these days. Very few writers have the leeway of Ken Follett in their ability to churn out a 1,000-page historical. And few agents will represent such novels, particularly from debut novelists.
In the end, I believe the majority of historical novelists strive for accuracy but are human and make mistakes. Some care more about their research, some less. We've mentioned both extremes here, so no need to belabor the point.
On a final note, while I believe criticism is essential to being an artist and every artist must learn to both accept and deal with negative criticism, I've seen some rather questionable things done to authors under the guise of criticism. I know of some writers who have been, in my opinion, unfairly targeted, to the point of having their books torn apart via reviews at online bookstores and other places on the web. I'm all for freedom of expression, but where do we cross the line? I often ask myself, if we were at a cocktail party and said author were there, would these people who hide behind avatars and other e-disguises be so bold as to go up to the author and berate their work to their face? Somehow, I doubt it.
This is not to negate criticism, which always has its place, but in this age of internet permissiveness, where there are literally no consequences for one's actions, thoughtful reviews which take into account a book's good points as well as its flaws are becoming less common than derisive, even contemptuous commentary, where delight seems to be taken in wrecking an author' efforts. This is one of the reasons I greatly appreciate the efforts made by certain bloggers to offer coverage of historical novels that includes honest, insightful reviews intended to inform a reader of a book's merits and/or faults.
I may be wrong, but in my experience no writer sets out to write a bad book ("whimsy" aside

. No historical writer, in particular, wants to get caught with his or her pants down having made a historical error. Writing is very hard, very demanding, and very time-consuming; financial rewards can be negligible, and publishers fickle. To survive, a tough hide is needed, certainly. But even so, there is no excuse for plain bad manners.