One detail that stood out to me, that probably most readers wouldn't even notice but I did because I am a seamstress...
When Scarlett decides to make the green velvet drape dress, she decides that day, and they start cutting it out that evening. Then we are told that the next afternoon, she and Mammy are stepping off the train in Atlanta. I am not sure how long a 25-mile train ride would have taken at that time, but I'm guessing they had to leave Tara that morning. So that means they made an entire dress - and a bonnet besides -- in probably less than 12 hours. Even with a modern sewing machine it would take at least that long to make a voluminous dress like that, much longer sewing by hand. So, although it's not said, Scarlett must have drafted every single woman at Tara to help -- Mammy, her sisters, Melanie, probably even Dilcey and Prissy. And even then, they must have been up most of the night sewing.
An unimportant detail, I know, but one that definitely caught my attention given my background.

Oh, another thought.... One thing that surprised me was Mammy's quick willingness to help Scarlett steal Frank Kennedy from her sister Suellen. She was always trying to pound lady-like qualities into Scarlett, so it struck me as uncharacteristic for her to be such a willing assistant in something that Ellen O'Hara definitely would not have approved of. Maybe it was just because she was so relieved that Scarlett was going after Frank (who was a gentleman in Mammy's eyes) rather than that no-good Rhett Butler (of course, not knowing Scarlett had been to see Rhett).

Last night I read the scene where Rhett comes to talk to Scarlett after he's out of jail and she's married to Frank Kennedy. Wow, what a powerful scene.......