Add me to the pile of readers who think Drag-On Fly would have been better minus 200-300 pages. Normally I don't hold it against an author when the book is full of padding that doesn't advance the narrative, extraneous "character moments," even Moby Dick–style long-winded explanations. The Harry Potter series has some of the best padding I've ever encountered, stuff that would sink the page-to-screen translation like a lead weight—e.g., the subplot involving Hermione's Society for the Preservation of Elvish Welfare.
Gabaldon's extra padding in D in A does us readers the great service of making 18th-century Scotland that much more real, through all the senses, right down to the smells of the malnourished and malprovisioned Jacobite Army. But there's too damn much of it. Nonetheless, that multi-sensory approach is one of the aspects in which the quality of the writing took a quantum jump over the first Outlander volume.
Question for those who know: When the Scottish characters don't speak consistently in their dialect—e.g., alternating between can't and canna—is that authentic, or is it just Gabaldon forgetting?
Gabaldon also seems to have exercised more caution in exorcising some of the anachronisms that litter the first book. Some easily forgivable anachronisms of dialog remain; I can't cite any examples.
Those who complain about the structure—scenes of Dr. Claire Randall, her daughter Brianna, and a grown up Roger Wakefield in 1968 bracketing 800 pages of flashback—also make a good point. I take issue mostly with the changes of POV between sections of a chapter, between Claire's first-person and a third-person limited omniscient through Roger. Nice try, Dr. Gabaldon, but it didn't work for me.