assessor's

[John Johnson]

is the county assessors a good reference for determining the actual value of a property?  

[Kyle J.]

Not usually.  The tax assessor's assessed value could be close, or it could be way off.  The tax assessor has likely never even seen the house, much less the condition of the inside. 

Also, in some states (like mine), there is actually a law (Prop 13) that restricts the increase of property taxes.  So if someone has owned there home for a long time, there could be a big difference in what their home is assessed at vs an identical house that was just purchased next door.