In my experience, the quality level of ads has dropped considerably. My last two Craigslist experiences:

I recently tried looking for a used car in the Chicago area. It turns out almost all the postings in the "by owner only" area are actually dealers in disguise. I found this out the hard way after driving an hour to see a car at what turned out to be some kind of sketchball dealership.

Another time, someone posted an ad for a musical instrument. I go to the guys house and he turns out to be some type of dealer/wholesaler. He didn't even have the actual instrument from the ad and was pulling some bait-and-switch crap.

All of this has pretty much soured me on Chicago Craigslist, but I will say that the experience is probably still a bit better in smaller metropolitan areas.