This kind of user testing (even done informally without a usability lab, eye-tracking software, video cameras, etc) is so valuable that I'd venture to say EVERY site owner should take a stab at it of some kind. One half hour should generate at least a couple weeks of upgrade work for most sites.
This is why I so highly value (and pay big bucks for) Jakob Nielsen's published studies - they are not just his "ideas". They are the results of his consulting firm's rigorous tests with very real, ordinary users. For those who don't yet know Jakob - get going! He was a key player at Sun Microsystems in developing the human/computer interface. And his no-frills website at UseIt.com [useit.com] is a true gem.
If you don't feel you can afford the cost of his full testing reports, then at least spring for his awesome book, Homepage Usability: 50 Websites Deconstructed. It lists for $50 but you can find deep discounts. That one book will make you thousands!
PS - Jakob was a celebrity site owner who once received a well-publicized Google penalty
for hidden content and keyword stuffing. He was just trying to get all the misspellings
of his own name onto the page.