What surprised me about this scene is that they don't talk. The book mentions that Darcy chanced upon Lizzy many times while out walking (to the point that she found it odd that he kept encountering her--a clue she missed, IMHO), and would walk with her. I thought this scene could've shown that bit from the book, but since they don't talk, instead of showing Darcy's increasing attentions to Elizabeth, it shows him as stiff and forbidding.