This use to be the go to way of advertising your items for sale. There has been many safety concerns with it though. Its a very impersonal way of selling. I prefer local for sale pages on Facebook now to kijiji. You usually have admins who get to know it's members and ban people who sell improperly. It's slightly safer in that you can take a look and see if their Facebook page looks real and that they are real people. I also find the search engine in kijiji is terrible and gives you many irrelevant items.

like any other site, it all depends who is posting, what kind of person they are and what they're willing to help you with.
for the most part I've had a great experience both buying and selling. the site is super organized and well-maintained