I had a name mismatch between my mba.com profile and all my IDs. My profile has "firstName lastName", but all my IDs have "firstName middleName fullName". I didn't realize this until the night before the actual exam and was worried that I wouldn't be able take the exam. But, fortunately they let me take the exam even with the mismatch.
It seems like middle name doesn't matter that much. Just wanted to let everybody know about it because I was freaking out last night after reading multiple stories on the forum.