Never used it m'self. My older brother used it but it didn't help him at all. He got a job as a Mechanical Engineer through a friend my oldest brother had.
I just typed in "Geophysics". The job layout is very similar to
www.usajobs.com except I'm sure that a lot of these are contractor or company jobs as opposed to gov't oriented.
Employers really like the folks who go out and meet them at career fairs and what-not. Nothing against internet applicants, but direct appearance right before them is more admirable in their eyes, often. But some of the time, online application is the only option. I'd say do it whether prospects look good or bad. If you're heading into the job market, even just for internship, having lots of extra folks reading your credentials and resume is always a good thing.
If you're concerned about privacy, I wouldn't worry. Only employers can peruse your information. And only ones that you apply to. You upload your resume and if they are curious, after your request for employment/interview is sent (through some option I'd imagine), they can view your resume and information.
Jam it back in, in the dark.