I'm no engineer, but my thought is that the 128-bit memory bus will be as much a limiting factor in 3DMark2003 as it is in everything else.
The frustrating thing to me is that the GeForce FX is a technology spectacular hampered by comparatively poor memory bandwidth.
I have no doubt that in terms of raw processing power and capability, the GeForce FX will have no equal. At the same time, you can put a Ferrari engine in a Yugo and...Still have a Yugo.
ATi definately did an excellent job anticipating where the market was heading and putting a chip of less power out and designing a better method of feeding it.
Unfortunately GFX is trying to suck a golfball through a garden hose...And predictably looks like it will just end up sucking.
I'm still very anxious to see non-jaded real-world user reviews on the GFX though.