I am curious. Where are you in Atlanta that your property value has not dropped? I have done comps for months all over the north metro area and I find that values have dropped 4-10% everywhere I look. I would love to take my Buyers to an area where values have not dropped.
As far as the loan goes Cameron has a good point about the cost of refinancing. But, like Cameron suggested, that math only works though if the ARM were to stay at 6% or less. If the rate on the ARM were to rise significantly after the 2 year period, which it definitely could, then you could end up in much worse shape financially at that time.
If it were me, and I have become much more conservative over the past couple of years, I would want to lock in to a fixed rate and not have to worry about market fluctuation. Even if I planned on selling near term there is no guarantee that I can get the price I would want, or a qualified Buyer, in the current economy.
I also agree with Elo that you don't want to do this with just any lender at this point. Make sure you do your homework and get references from the lender and examples of recent successful loans they have brokered. Talk to others that have just closed loans with this lender. The may be rushing you because credit and available capital to lend is questionable and may not be available soon or it may just be because they have not had much business and they need a paycheck.
Good luck to you whatever you decide.