It might not be the entire explanation for why the economy has been sputtering recently, but it appears to be a part of the problem
Sometimes government stimulus efforts can do more harm than good. In a purely cyclical recession a confidence boost by the government can often help. If it improves the sentiment of businesses and consumers, then their spending won't decline as much and fewer jobs will be shed. But when a government action tries to act as a temporary remedy for a severe structural problem, it might just get in the way of the economy finding its new equilibrium and make matters worse. The home buyer credit appears to be the latter type of stimulus measure and may be part of the reason why the economy hasn't stabilized.
Knowing precisely the affect that the home buyer credit had on the economy isn't easy. It likely increased home sales and prevented some layoffs, but only for a time. After the credit disappeared in May 2010, home sales plummeted and any layoffs that were initially prevented would have occurred anyway. But for the year or so that the credit was in place, it stimulated the economy. Here's a chart that estimates the effect of the credit on just residential investment: