An interesting article from Jeff Sauro in which he talks about how important the first click is. His research indicates that when the users' first click is down the right path, 87% eventually succeed. When they click down an incorrect path, only 46% eventually succeed.
Jeff outlines a few techniques you can use to measure the effectiveness of routes through your site to key content. When you consider that for each audience there is a small handful of tasks that are significantly more important than the rest, this kind of website appraisal is well worthwhile.
Getting the first click right - article by Jeff Sauro