DDR RAM still is supposed to be about the same price as SDR RAM. From what I've read, the manufacturing costs are only 5% higher, and so the end price should be only slightly more expensive, too. The prices at the moment don't say that much, wait till the first mobos are available and more people want to get DDR.
But I feel with you, I also wonder if I should use DDR RAM. On the one hand I do not want to wait till early February (and, me being in Germany, that'll rather be March ...), on the other hand it seems as if the DDR boards would have a pretty good upgradability. Oh well.