As I've posted before, I think many cis women m/m romance authors write good male viewpoint, and many have a good understanding of issues gay men deal with. And then there are those books where I start to wonder if the author has ever actually met a gay man. I probably excuse more in slash fiction, because some of those writers are young and they're learning by reading each others' work. There are original fiction authors I can take lack of realism from and some that I'm mentally harsher on, because they could have done research and talked to gay men.
I give most cis, straight women readers credit for realizing that some of the books they're reading are total fantasy, but I wonder about some readers knowing enough to know what's fantasy and what's more realistic, considering that some authors don't seem to know. I don't name names of ones I think don't know, but some of the participants in the AfterElton (now The Backlot) Gay Books forums gave their opinions about what seemed unrealistic to them.
There are the "Gay for You" and "Suddenly Magically Gay" tropes in original m/m fiction, which I think come from slash fiction. Some readers eat those up. I can only take it from certain authors.
I'm taking a lot of book recommendations from the AE/Backlot romance readers.