It really does depend on the situation, as every one is different, but truthfully it depends more on how well your home is priced.
The situations where appraisals are coming in low are when sellers have too high of expectations, and buyers are submitting too high of offers JUST to get into escrow right now.
If your home is priced well in comparison with your local comps, it shouldn't be a problem. Remember, banks ARE very conservative right now, and are only looking at things like upgrades to a certain degree.
Beware of anyone that tells you I CAN DO ANY DEAL IN 30 DAYS....and vice versa, of someone who is not optimistic about helping to sell your home.
Remember, anything can happen, so give yourself an advantage by KNOWING how much your home is worth before you list it, or even further putting it into escrow for a few weeks.
Best of Luck,