Yeah, I've heard that some of the demos aren't that great. Call of Duty 2 looks wonderful, but King Kong leaves much to be desired.
It's alright though. All console games start out "bad" and as time progresses, they get better as developers learn to fully utilize the hardware. Look at the Xbox...Halo's graphics weren't that great (although the gameplay and plot were extraordinary), now look at Splinter Cell: Chaos Theory, Halo 2, or FarCry Instincts...the graphics in those games are at a level never seen before on the Xbox. After FarCry Instincts, I have some confidence in Half-Life 2 when it comes out in less than a month.