If you haven't owned a home in the last three years you are considered a first time home buyer. The $8,000 tax credit that the goverment is offering will only be available until November 30th of this year. Buyers need to get in there and buy now. Interest rates are at historical lows, prices are great and a tax credit to boot!
Income thresholds, $75,000 for individuals and $150,000 for joint filers. After those limits the credit begins to phase out. If you bought a home this year and expect your income to be lower than next year's, it makes sense to file for the credit this year using a 2008 amended return.
Go for it!!