I'm a little late to this, because of travel/booksigning woes, but I did want to jump in and offer a few things here. As Lyn said above, the AMA isn't often going to be able to dig into details about what was in the original draft--that's the sort of thing we like to keep a little closer to the chest. I'm okay with revealing things like that in the abstract, but having a wholesale "let's reveal plot points in early drafts of books without context" reveal seems like it might be dangerous.
So here, off the top of my head, are some of the things that I changed in the book related to Beta Reader comments. These topics are "open" for discussion--meaning you can ask Betas for more specifics on them, if you feel like it. These were all things I changed specifically because of Beta interaction.
Adolin's viewpoints were added to Part One. As was a quick run-down on Renarin's powers, and what he was learning to do with them.
The romantic angle between Shallan/Adolin/Kaladin was tweaked as I more and more referenced the idea that two different personalities of Shallan's were in love with two different people. IE--moving it further away from a love triangle, and instead showing more clearly that that Shallan was splitting further into multiple people, with different life goals.
This wasn't coming across in the early drafts, though I sometimes coulen't quite tell which responses were knee jerk "Twilight ruined love triangles! Don't do them!" comments and which were "I'm not convinced these four people--counting Shallan as two--are actually working in relationships." (I'll note that I, personally, am very pleased with how this part turned out in the books--but the betas certainly helped me get there. I'd guess that this is one of the more contentious matters of fan discussion about the book. The point of bringing it up here isn't to discredit anyone's feelings about the actual arc, just point out how the betas helped me find the balance I wanted.)
I got a LOT of help from people for writing Shallan's getting drunk scenes.
Slightly beefed up Yelig-nar's part in the plot, as what he did wasn't coming into play enough--and originally (I can't remember if this was a beta thing or an alpha thing) he wasn't as involved in the Amaram/Kaladin fight.
I revised part four heavily, moving the scene where Kaladin runs into our "so very beautiful" friend from Elantris (and the subsequent dip into the Spiritual Realm) from happening in the market to happening in the Lighthouse. Originally, the Lighthouse was run by Cryptics. (Which was a lot of fun.) However, I needed stronger establishment of Kaladin's motivations earlier in Part Four, which was going kind of off-the-rails a little.
Lots more conversation between characters who weren't talking enough in Part Four. (Most specifically Azure.)
There are hundreds more, but those are a few that might be of interest--and I need to be up in three hours to get on a train to go do more signings. Jet lag sure is fun!