Part 1 of my review: It is all about the stats.
Yes, we need to be numbers people to provide some information to our clients - and that too, very quickly.
Based on what I have seen of TerraDatum, I think this is an excellent service they provide. (Make sure your Zip Code is included in the research.)
As per their tagline - it is the market analysis and matrics for the real estate professionals.
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Disclaimer: I am not a subscriber to the Terraditum services.