Lora, the $15,000 would be going forward, after the bill is enacted.  The amended $7500 tax credit was initially a 15 year, zero interest loan, now it will be a true tax credit not to be repaid.   The 2008 American Housing Rescue and Foreclosure Act is what they are amending.

Tom,  I would consult your tax accountant on that question.  My guess would be that it would qualify for the $7,500 tax credit that was amended and not the $15,000 because it has not been enacted yet.  Once again, that's my guess.  

Jason, You are correct on both counts.  The tax credit will offset, dollar for dollar, any tax liability you have.  The tax credit can also be spread over two years if your tax liability is not as large as the credit.  

Jason, I've been scouring the news feeds looking for that answer.  So far everything I've found says it was axed from the final version.  The only thing I have found is the previous $7500 first time home buyer tax loan will be converted to a true tax credit.  I have yet to find anything that states it will be extended to the end of the year.  I'll create a post once I've got the final version.