I Zillow'ed both of my properties.... I seem to be doing just fine.....
My rental house(next door to Mudd's condo) is valued at about 60% more than I have invested in it. I bought it in deplorable condition for not much more than the price of a luxury car, put about $40,000 in it and it rents pretty easily these days.
My house near the RTown/Inman Park Marta station is still Zillow'ed at about $50,000 more than I paid for it in September 2007 in a foreclosure sale at the very beginning edge of the financial crisis......Thank you baby Jesus that I am cheap and can see the potential in a broke-down shack.