Outlander is a very well researched book with a compelling story line, and Scots should be very grateful to Gabaldon for taking Scotland on this wild literary ride. That's my disclaimer.
This is my defense: I think the reason I stick so close to home with my books is that I don't feel comfortable trying to convey the idiom of a culture I am not intimately familiar with. For instance, I would never embark on a story about the American South, because that rhythm of speaking just isn't available to me. I know what it sounds like, and I could sort of imitate it, but unless I lived there for a lengthy time, I wouldn't be able to access that particular cultural idiom. I would be depending on caricature.
I was born and grew up in Scotland, so I have an advantage when it comes to Scottish dialogue. I know the metre and rhythm of Scottish speak, what the silences mean, what the glances between Scots amount to. I know, for instance, that beneath their thousand year old allegiance to the church lies a deeper more persistent drone, that what they really fear is themselves and their own history.