Maybe true - but in a year or two cards with that level of performance will be a lot cheaper, so it's a question of what, if anything, it's going to win now.
Although I like ATI cards, getting a 4870 doesn't seem like a good deal - simply because it doesn't seem to offer much perfomace over...
At the moment, I've got a 9800GTX+, and it seems to run all the games I want at reasonable framerates on my display (OK, Crysis is a bit choppy if you turn everything up).
Assuming I have no immediate intention of replacing my monitor, does replacing the 9800GTX with a 4870X2 make any sense...