If your CAD software doesn't need you to rotate an image, then a slow speed shared memory video would be ok. But if you want faster zoom, rotate or animation you must get a decent video section.
There's another side effect of shared memory video. The CPU loses some speed since it must wait if the video memory is being used. I've seen from 5 to 30% speed loss over dedicated video systems.
How important is it to have dedicated graphics memory when using CAD software. Is it a must? If not would you recommend the Fujitsu S6000 series notebook?