Interesting. I looked at my house, and the value is fairly close to what I expected, about $25,000 low based on my market analysis. I'm a former real estate broker and my son is a professional appraiser, so I have a fairly decent knowledge of how to do an analysis.
The program correctly identified my house as a 4BR/3Bath, got pretty close on the square footage and nailed the lot size.
However, the mapping was off by more than a block. The house they identified as mine is more than a block South; when I scrolled up to the actual aerial photo of my house, they had a much lower price on it, and had a higher price on the 2BR house withut a pool, next door to me. So, there are some serious flaws.
It's a fun tool to start a valuation, but I would strongly recommend that it not be the only tool that is used.