I think the book differences are another case of what working in a book not working on screen. Dwarves crossing a river one by one is just a couple of lines at most on the page, but is likely to send the crowd into purgatory by the time the third dwarf sets across, and by the time they get almost done the crowd will be angrily checking their watches and asking for refunds. And people call these films padded - they don't know how merciful PJ is.
I wonder if Bombur will talk at all in the new scenes. Since he's asleep I guess not. I know he spoke during the troll scenes, but so did everyone else getting cooked on the spit so I'm not sure it counts. I'd like a line, at least. Or maybe just keep him silent but ramp up his action set pieces to hilarious levels to compensate (barrel ninja pt2). The unsung hero of the movie, who never says a word. At least it's better than Tolkien, who basically used Bombur as a walking source of fat jokes.