Remember that an appraisal is closely associated with what similar homes have recently sold for, and as such it does not take into account upcoming changes in prices (if any).
I mention this because Reuters reported yesterday that Alan Greenspan (former head of Fed) expected "much lower" prices as ultimately we get rid of the oversupply of homes for sale.
While we may have different opinions of Greenspan, I like to listen to old grey-haired dudes with tons of experience in auction markets (and who are not tied to the market in question).
So regardless of what the appraisal is today, how will you feel if a few years from now houses similar to yours are selling for X% less than you paid?
-HW "Skip" Weldon Columbia, SC