Per the IRS, ONLY the changed Forms/Schedules need to be attached.
But the 1040 DOES change. 🙂
I guess the consensus is that the 1040 is NOT required, but I agree with George, I include it anyways. In some cases it can contain important information that is not on the 1040X, and may help the IRS agent process it. Plus my software prints automatically prints it, so I may as well do something with it. 🙂