Most free domain appraisal sites are inaccurate, and out of all i have tried estibot.com is easily the best. I've been using it for a few months, and the appraisals are generally similar to how much the domain can be sold for. The only weak spot i have noticed is that the prices for 4-letter domains (and shorter) are lower than what you could actually get for them
Yes estibot is great. You can view their friends page and see us listed.
Thats neat - and its good for seo aswell (estibot.com has a pagerank of 4)
The portfolio appraisal tool is handy aswell
The owner of estibot.com has obviously put alot of effort into the site
Its a great site. Theres no competition really, sites like leapfish and dnscoop are way off the mark when it comes to appraising domains accurately