Yeah, your screen would be blank without a graphics card, and you'd be looking at your own ugly mug in the screen, we know. I think the original poster's question is basically:
Yes, I know the MacBook's graphic card is so unspeakably awful that it might as well be a dead rat glued to my motherboard. But what affect will that really have on my ability to use the computer? What applications would have a performance penalty?
I think its an interesting question, and want to know the answer too. In my opinion, most apps would work fine except 3D games. You may also want to check in with some places that specialize in benchmarks, like BareFeats and see if they compare MBs and MBPs at specific applications.