Pierre - Craigslist is definitely better some places than others. I'm guessing most of the Canadian craiglist sites are still pretty low traffic, while San Francisco is gigantic (it's the original Craigslist and probably close to 10 years old) and many of the other US ones are also pretty big.

We've had some postings get no responses and some get almost a hundred applicants for similar jobs. I would suggest that the way your ad is written makes all the difference in the responses you get.