It's free to post, you don't even need to register. I just sold 2 things on there this week(an old lawn mower $25, and a ridgid shop air cleaner $60), and no problems. I only deal with people in person, and only let them know where I live after we've gone back and forth a few times in email or on the phone.
The funny thing is, most of the folks I've been dealing with are using their work email addresses, and I'm able to get an idea of where they're at ahead of time. I only accept cash or trade.
In my opinion, its no different than the classified ads in the newspaper, just a whole lot cheaper, faster, and you can edit your ad on the fly.
I highly recommend NOT using your primary email address. If your internet provider gives you multiple email accounts, set one up just for Craigslist, so you don't get spammed.