“Oh great! Just as I had figured out the 2008 first time home buyer’s credit, they go and pass a new one with different rules!”
Here are two handy-dandy resources from NAR that will help you make sense of it for yourself and your clients.
First we have a slide deck in PDF format (300K) explaining the details of the 2009 first time home buyers credit.
Lastly, here’s a one-page chart (300K PDF) explaining the difference between the 2008 and 2009 versions of the first time home buyers credits.