I have a book I'm reading through. I saved it in my favorites folder. Under 3.X I would have to continually save it to the Favorites Folder or remember to bookmark it or i'd have a difficult time finding my place. Not anymore! I saved it once which opens it to the original bookmark, then just select the last gray dash. End of story! Thanks Logos!
If one more category of marks could be added I would add table of content marks that could be turned on or off. A mark on the scroll bar would represent a new chapter. I'm sure the majority opinion though is "Just what we need, another color on the scroll bar :-)"