One reason the soon to come Realtors Property Resource (RPR) won't workbe any better than Zillow is because it will rely on real estate agents being accurate and consistent in how they define property characteristics. I'm not just talking about calling a small house cute, but actually getting the factual details correct.
Chicago real estate agents will often list a property as having a garage space when the reality is there is a garage space for rent down the street. Many agents don't know the difference between a level and a floor. And what some agents label a "Bedroom"... don't even get me started. All of these are examples of the kind of bad data that will cause havoc in an automatic valuation model. MRED (the Chicago area MLS) relies on agents self policing the data for accuracy, but that's like the fox guarding the hen house.
Valuation models are great (I build my own), but if the people using them don't understand how and why they work , and real estate agents don't, they won't work.