I've used Craigslist a hand full of times but I am always careful. Whether I am selling or buying I always make sure to never met where I live or at someones house, I always request to meet in a public area like a shopping mall parking lot, if the person has a problem with that I do not bother going further with the exchange. On the side I also never go alone and let someone else know were we are going and for what. It might sound a bit paranoid but it's just normal precautions to take in many situations.
No. Craigslist is not to be trusted. There are always exceptions, though. If you do it in a public place it has a higher chance of going well, depending on the person. I do not like people coming to my home. It is a great way to find things you normally wouldn't be able to easily. There are plenty of ads that are actual stores to go to, so that's helpful as well. But I would never trust it.
I've used Craig's list to purchase furniture before. I think it's great to get High quality pieces at great prices. I have a few friends who have sold furniture when they moved and couldn't take it with them. Other then that I look for tag sales on it and have apied to a few jobs. I think it's a good site to find things you need but I really only use the furniture, jobs and tag sale links.