Here's What I Can Do for You ...
What is the value of a good interview? A job offer.
Although it is possible to have a great interview and still not get the job, the opposite pretty much never happens. It is virtually impossible to perform poorly in an interview and still get the job.
To do well in an interview you must be prepared, and in order to be prepared you first must understand the purpose of an interview. I know that sounds rather elementary, but before you read further, see if you can sum up in one sentence what you believe to be the purpose of an interview.
If you said something along the lines of "to learn more about the applicant" you would be only half right. You must add "what can this applicant do for our organization?" in order to get full credit.
Failing to recognize that the question "Tell me about yourself" actually means "Tell me what you bring to the table and how it will be a benefit to us" can be a fatal error. One of my biggest pet peeves when I am interviewing candidates is being treated to a litany of reasons of why my job would be good for them, rather than the other way around. I have had candidates tell me everything from wanting a better schedule, a shorter commute, solving daycare problems, gaining new skills or just assuring me that getting this job will help them to fulfill their "dreams."
Now I am not so naïve as to believe people don't have personal reasons for seeking a new job; it's just that sharing those reasons is not a great marketing technique. How would you react if someone tried to sell you their services by informing you of what the sale would mean to them rather than what the service they provide will do for you?
I'm not recommending that you don't take the opportunity to "blow your own horn" during an interview. By all means, blow it loud and clear! Sharing accomplishments are different from sharing needs. Be vocal about what skills you bring to the table, but be clear how you can use those skills to benefit the employer.
Keep in mind that if you want to land the job, it ultimately boils down to what they need, not what you want.