I'm happy to see that there is FINALLY a 4870 1GB review. Seems like the extra memory helped at high resolutions overall, but for the price, I don't know if it is justifiable. The GTX 280 is just starting to hit the upper $300 region after rebate, and overall outperforms the 1GB 4870, but these are very early judgments, and perhaps other reviews will point to the 4870 1GB in favor.
My overall opinion is if you want something that is more powerful than the 4870 or GTX260, then the GTX280 seems to be the better deal, and the 4870X2 if you want the best single card solution.
EDIT: Features are also a selling point, don't forget those.