First of all, it's a mobile CPU
Second, it's about as powerful as A Pentium M 1.4ghz. Everyone knows you don't compare a Pentium M to a Pentium 4 in performance, just like you can't compare an Intel CPU to an AMD CPU directly based on stats, you need benchies. Lastly, it's three years old and was at the end of it's cycle. Just wondering buddy, what's your system like? Those who live in glass houses don't throw stones.
Moving along ... what I said is plain true. The X1900XTX beats the 7800GTX 512 in all games except for BF2 I believe, or that FPS that was heavily optimized for Nvidia. Even when it does lose, the X1900XTX falls short of a FPS or two. Also, the X1900XTX is around $100 cheaper. ATI's X1K series cards also have better image quality than Nvidia's Geforce 7 series. I read in an article a few months ago as well, that the 7800GTX 512 has a "lifespan" half of it's "slower version", the 256mb version.
And don't think this is bias, because I usually find Nvidia's cards to be better.