I think Zillow gets the nod because they were first. I've found them to be very accurate on some ocassions, miles off on others (I sold a house 2 years ago that Zillow said was $1.2M...my buyers got it for $514k...either I'm REALLY good or Zillow was off on that one).
I think those sites can give consumers a good starting point, simply by comparing home statistics. Nothing will replace actually viewing the home, though. Specific location (down to the lot), interior features, quality of finishes, etc. You can only get that value by seeing the homes.
I think that's one area that a good real estate agent can add value. When you're looking to sell, does your agent simply bring in a paper-work home valuation, or do they offer to drive you around to view other comparable homes for sale and drive by comparable homes that have sold?
For a starting point, though, these sites are an okay tool.

I think Zillow is OK for getting a general idea of the home prices in the area.

If I were looking to buy a home, I would use the information to help me determine the purchase to rental ratio in the area.

That ratio should give me a good idea if the houses in the area I am looking at are overpriced or not.

I just checked the ratio on a rental house next to UPS. The ratio was 21.9.

This tells me the Zillow estimate of $290,000 is pretty accurate. And the house is actually fairly priced.

Zillow is outstanding and getting better by the month. We placed them on our website recently since their pricing has become more in line with recent sales.

Their web traffic is Huge and not to be ignored. A merger with Zip is supposed to happen or watch for them to be gobbled up by another Big player!

Ray Pepper
www.500Realty.net

Everyone knows that Zillow and all these other "home valuation" sites are just rough estimates.

The true value in them for a home buyer is being able to easily map out comp sales nearby and compare home stats all in one page. It's much easier than entering each home address into the county assessor tax site.

Zillow does not do well with properties on acreage, waterfront or with views. Nor is it particularly accurate in N. Tacoma where in the past I've seen comps on S 12th used in comparison to a home on N 13th.

The do in homogeneous neighborhoods such as The Heights in Puy, or in DuPont.

After trying Zillow a few times over the last two years, I am recommending that they are inaccurate with their pricing. Most of the agents (apprx. 40) is the real estate office I was with before I went independent were in agreement with me. I appreciate any website that gives accurate and current info. It still boils down to getting a Professional Real Estate Consultant to help. Be it an agent, broker or advisor with experience!
Larry Tutino
Mt Rainier Properties
mtrainierproperties@gmail.com