Refi's don't count.
The 1 Jan 2009 and later $6500 tax credit is strictly a credit, it needs not be repaid.
The April 2008 - 1 Jan 2009 $7500 credit, that you would presumably be entitled to, does need to be repaid 1/15th at a time, interest free, over the next 15 years.
Here are the other disqualifiers:
Your income exceeds the phase-out range. This means joint filers with MAGI of $170,000 and above and other taxpayers with MAGI of $95,000 and above.
You buy your home from a close relative. This includes your spouse, parent, grandparent, child or grandchild.
You stop using your home as your main home.
You sell your home before the end of the year.
You are a nonresident alien.
You are, or were, eligible to claim the District of Columbia first-time homebuyer credit for any taxable year.
Your home financing comes from tax-exempt mortgage revenue bonds.
You owned another main home at any time during the three years prior to the date of purchase. For example, if you bought a home on July 1, 2008, you cannot take the credit for that home if you owned, or had an ownership interest in, another main home at any time from July 2, 2005, through July 1, 2008.