Congress is in the process of reviewing the 1st Time Homebuyer Tax Credit. The way it was passed for 2008, calls for a payback over 15 yrs at zero interest, with payments starting the 2nd year after purchase. Since nobody has even gotten any money yet (since they would get it with filing of 2008 Income Tax ) it is still possible that the government may restructure this program. Under the current plan, each year, as the buyer would file their income tax, they would repay 1/15th with their income tax.
Assuming most people get a refund each year, the assumption was that if you would have gotten say- $1500 refund normally, your refund would be $500 less (to pay back your years portion of the tax credit) but you'd still get $1,000 refund.
There is a possibility that this tax credit will be modified - and possibly have the repayment eliminated - or have it made as a "forgivable credit", ie: if you live in the home as your primary residence for say 3 yrs it wouldn't need to be repaid. We won't know until it finally gets passed.
But, for someone who is in the market to buy, finds a good deal, and has the financial means to do so- there are some wonderful buying opportunities. Just make sure you get good guidance from a knowledgable Real Estate Professional in the area you are going to buy.
All the Best!