Note that the data is spotty, and this service is considered in beta right now.
From the WSJ article below:
“Over time, Zillow hopes to have solid estimates for all areas. For now, though, it works best in metro areas like Seattle, San Francisco, Phoenix, Los Angeles and Cleveland. Results are weaker in metro areas like Boston, Philadelphia and Chicago. And they are weaker still in metro areas like New York, Houston and St. Louis.”
Further evidence that agent’s value proposition is moving further from access to the data and more towards expert knowledge and fiduciary service.
This article on the Wall Street Journal has some good information about the service.