For most purposes, when it comes to hooking up a deal with "active buyers", a large part of that "buyer's market" bases their decisions on verifiable/reliable traffic stats - paying some multiple of the traffic earnings.
I'm not voting in favor of the traffic stats model of valuation, as I don't believe it represents full and fair value in many cases, but appraisals that are not based upon traffic data will get you little more than scornful replies in most domaining forums where active buyers hunt for bargains.
No you don't. Most the time those are people that own appraisel companies who have no intention of buying your site. Complete waste of time. Anybody buying domains knows what they are worth. It is worth what people are willing to pay for it.
There is also the consideration that the appraisal company may appraise it low in hopes they or one of thier buddies can buy it from you and then resell it.
I tried a major auction sites top appraisal package a fews years back and it was a total waste of money. The 10 points they provided was from a standard template with nothing changed in it to reflect my domain. All just generalizations that could be applied to any domain.
As I was reading I remember thinking how I could not believe I paid for this garbage and how much more valuable the information posted in threads at webmasterworld is in accessing a domains value.
Valuation of domains is based on pure speculation. The guess of an "expert" is often little better informed that the guess of a lay person. The pruchaser typically has the best idea of the value as they are the only ones who know what they're going to put under the hood.