Assessments have always been and still are all over the board. For that reason we are still seeing some homes selling over and under assessed. Appraisers put most of their stock in comparable recent sales. We have seen some potential sales not appraise in this market and price adjustments are needed to get financing. Appraisers are being very strict in this market climate.

Assessments have nothing to do with the value of your home. Most communities only do physical assessments every few years, and the majority of these are done without going into the property. They are just a way for the City/Town to make an evaluation for property tax purposes. These are based heavily on public record information (much like the big search site guesstimates) and don't reflect the true market value of your home.
You need to use the most current (within 3 months in this market) sales data on comparable homes within your community. An appraisor will base his report heavily on SOLD and UNDER AGREEMENT properties. These reflect the prices that the market is willing to pay or make an offer on and will give you a much better idea of what your home would sell for.
Appraisals have been coming in lower in recent months than usual for a variety of reasons ( short sales,foreclosures, tougher underwriting rules etc...). Many are coming in under the accepted sale price, meaning the Seller has to come down more , the Buyer has to put down more or a combonation of both.

Good Luck!

The assessment has no bearing on the appraisal value of the home, in the eyes of the bank. Although it can actually help in reverse. If you get an appraisal done, and the value is below the assesment value. I have had borrowers take the appraisal to thier town/city hall to reduce thier taxes.
If your a buyer and the appraisal come in below the selling price. This is the perfect tool to helping you renegotiate another sales price.