I'll weigh into this discussion.
I recently bought a Macbook Pro with an Intel HD 4000 GPU to complement my existing one which has a higher spec option ATI Radeon HD 6750M GPU. They are exactly the same computer (identical CPU and RAM) except for the graphics cards.
Tried them out using a fairly intensive sketchup model (approx 30Mb) and could not tell them apart. Open GL, maximum texture size and hardware acceleration all turned on. Rotating the view was fine, maybe generating the shadows was a fraction slower on the HD 4000 computer.
While it could be a different story in a Windows system, for Sketchup running on a Mac the Intel HD 4000 GPU is fine.