sdrealtor, I disagree. The very best properties were on fire sale in the last downturn, and they will be again this time. (In my opinion, of course)
no_such_reality brings up a great point, and I agree with him. Let me give an example.
One of my favorite homes was purchased by a friend at 48% of the price of a comp that was sold just 18 months earlier. So she got 52% off just by waiting for the trough. I plan on finding hundreds of these types of deals in 2010.
To retain their anonymity, I will not give enough details that you can find them. However, they paid $ 96/sq ft, and the neighbor paid $200/sq ft just 18 months earlier. When I first met her, she told me they got a real good deal on their house, since it was purchased during the real estate slump.