I started to get ambivalent toward Night Moves in the middle when it spent too long not being a mystery, but it won me over in the end. And I didn't actually think the plot complications were hard to follow. Some points are ambivalent but it's not hard to fill them in with likely explanations. That doesn't mean I'll be able to explain it all from memory.
Looks like Ebert didn't agree about Jennifer Warren:
> The mistress is played by a relatively unknown actress and sometime singer named Jennifer Warren, who has the cool gaze and air of competence and tawny hair of that girl in the Winston ads who smokes for pleasure and creates waves of longing in men from coast to coast. Miss Warren creates a character so refreshingly eccentric, so sexy in such an unusual way, that it's all the movie can do to get past her without stopping to admire. But it does.
It also got a Great Movies entry.