The syndication resources of Postlets makes it worth using. You are aware, of course, that Postlets is owned by Zillow. A really good feeder system for them.
You will be well served to know who is using Craigslist and Zillow and leverage that information. You will realize the professional look is for the benefit of you and me, not the prime user of these sites. Use Postlets as a feeder to 'your zillow." Your analytics will expose the benefit and the need to anticipate the need of a typical CL and Zillow user.