Yes it is worth it. I found a freelance opportunity on the ProBlogger Job Boards - the pay was OK but after about six months, a new opportunity came along and the pay is fantastic. This new opportunity has led to even other opportunities - a snowball effect if you will. I've been with this other blog for over a year and the company even flew myself and several other bloggers to their headquarters for a brainstorming session. My blog posts have also been syndicated in several major newspapers which has helped me grow my personal brand.
I probably responded to a good 20-30 posts before I landed the first gig but it was worth it. I know that there are several other places that other MDC mommas have found useful in finding good freelance blogging opportunities but I don't have personal experiences with them. I'm sure they'll chime in, though.