Unreliable Narrators?

Time to revisit an age old debate among serious readers. How dependably can a fiction author use a narrator of the opposite gender?

For an opinionated person, this issue is fairly neutral for me. But at a meeting discussing "A Widower's Tale" (2010) by Julia Glass, I was reminded how strongly many people feel about this. Though the narrator is a 70 year old widower, Glass' gender never crossed my mind; I was captivated by the believability of her central character. Not so for several women at the meeting. Aside from questioning Glass' ability to accurately speak in a man's voice, they also said something I've often heard , i.e. male authors who use women as narrators fall short. I don't feel qualified to comment here, so any women reading, please offer up your examples refuting this. After reading any book you offer as an example, I'll feel more grounded in future discussions.

This gender discussion got me reflecting on a parallel issue. How dependably can a fiction author use a narrator not sharing their race? I clearly recall how moved I was reading William Styron's award winning novel "The Confessions of Nat Turner" (1967). Much later I was surprised, perhaps naively, to hear of the significant resistance Styron faced among respected black critics at the time the book was released and for years after. I'd be equally curious to hear your views on this, recognizing it could be more inflammatory than the gender issue.