I believe he was comparing the 8600 mobile version with an x1900 mobile version, where the 8600M is on par or just a little better then the x1900.
The x1900 mobile version is only better then the 8600M in OpenGL games. But they recently fixed that with a driver update I believe. (And the X1900 mobile version runs Hot as ****)
The 8600M (M is for mobile) is a mid/high end card surpassed by the new 8700M, which is a high end card. Apple had the choice of putting 128MB, 256MB or 512MB of Vram on the cards, And chose 128MB for the base model and 256MB for the high end model, so the MBP does come with 256MB.
Oh yeah... The 8800 only exists as a desktop part. And yes, off course the x1900 desktop card is better then the 8600M, It's a desktop card!
When it comes to desktop parts, I agree with Zepplin68.
"The 8600gt is not low end. The 8400/8500 series are low end. The 8800 is a high end card, and the 8600gt is mid range."
I've been waiting to buy my new computer since apple started using Intel, and therefore I have researched every GPU known to man. SO the facts written above are correct.