I had a great experience about 3 years ago. It was amazing.

First, SO Careers 1.0 came to a halt, they made a few changes in 2.0, they changed it to an invite-only system as opposed to a premium subscription service. They best part of all, they reimbursed everyone who had previously paid. Here was the blog post about it: http://blog.stackoverflow.com/2011/02/careers-2-0-launches/

It was great, I was getting several requests per week for a while, and it even helped me land a job across the country.

All that being said, I haven't kept my SO Careers profile up to date lately, and haven't had many inquiries in a while.

I do highly recommend it.