You mean if you manually overclock? I don't remember off-hand, but it shouldn't matter. If you OC with software, just rip the card out, and if you altered the bios, then just flash it back. It does have to have the stock cooler, though.
The caveats are:
-You have to do it within 90 days of purchasing the card.
-Some cards have long wait times
Also, the MSRPs for the new cards are ridiculously high in some cases. I think that sometimes you could do better if you bought the new card discounted somewhere and then ebayed the old one, but I guess there's less hassle this way, depending on how you look at it.