I visit doctorhousingbubble.com from time to time. He lacks the alarmism I see in some bloggers and more importantly backs up his predictions with vast amounts of data and research. From his end things are not yet bottom. And I think he's right because they've overall continued to decline. There are occasional blips, but in the grand scheme more people are defaulting, underwater, etc.
Also, if rates do go up meaningfully (they were at their historic lows a few weeks ago but on their way up again), they will inexorably lower what people are willing to pay for a house unless they are, along with the higher rates, receiving more pay. But as we know inflation is basically flat and pay raises are too plus most importantly unemployment is high and will stay that way.
There are numbers to support both sides but overall I think housing has not hit bottom yet, though even defining exactly what that is is hard since many things make it up from median prices to numbers of homes sold to homes in foreclosure, etc.
On CNBC today or yahoo finance it reiterated how the fed reserve come March will be cutting back its backing of loans, which is going to be one factor increasing interest rates.