Robert, with real estate, like any investment, you must consider you short and long term goals, when making a selling decision. If you sold today, would you be a buyer tomorrow? If you sold today, would you sit on the sidelines until you thought the bottom had been reached?
Personally, the only reason I would advise selling today, due to the market conditions, is because you have identified a better investment that you consider "cheap" at these prices, and so you want to move your money to that other investment. Think of it like selling Intel to buy Apple. You still plan to be invested, but you think there's a different investment that you like better.
If you plan to sell and then sit on the sidelines, there's a reasonbly good chance that when you decide to re-enter the market, prices won't be any better then, than they are today. You see, to know we've hit the bottom, we'll have to be able to see that bottom in the rearview mirror, which means prices will have been going up for a while.
And all the while you are sitting on the sidelines, you lose many of the other advantages that being a property owner have. Tax advantages come immediately to mind.
One final thing to strongly consider, with regard to selling real estate, is that selling is not cheap. With commissions and escrow fees, it's going to cost more than a $7 trade at Scottrade. And then when you buy again, you'll pay escrow and mortgage fees. Will this new bottom really be that much lower to offset those additional costs?
So my advice would be, if you plan to stay invested, then sell if you want to buy something different/better, but hold if you were thinking of sitting on the sidelines.