I found the Zillow.com site to be unreliable. I sold a house in December 2005 for $155,000, and Zillow.com lists the value as $124,000. I also checked several other addresses and found that the valuation was off on those too. But I agree, it’s still interesting to see what it comes up with.
The greatest value I have found in Zillow is its fast satellite view of the property to use in eliminating properties for location problems. It can prevent going out to preview/show properties and finding that they back up to a busy street or train track, while the homes on the other side of the street would be just fine. I have found Zillow to be faster than keyhole and other similar satellite view sites for this information. As far as pricing, while inaccurate market to market, it does show quickly the relative values of properties within a neighborhood or submarket, and I like the visual presentation of that information rather than lists of addresses on appraisal district sites.