there is a new Audyssey MultEQ FAQ and Setup Guide that brings new meaning and results to different mic patterns and rooms.
See here: http://www.hometheatershack.com/forums/audio-processing/68407-audyssey-multeq-faq-setup-guide.html
the specific parts that best apply to setup are in section (posts) 5 and 6.
Don't forget to click on "DO NOT OPEN... DO NOT CLICK THIS BUTTON! >>>>> SHOW" in section 6 for full details on mic patterns and the results.
since the time i bought my receiver, i was never satisfied with sound clarity in the center, whatever mic pattern i tried.
this article made it clear to me what i had to do to get the results i wanted, both for frequency response and imaging.
i used to have excellent frequency response, but the imaging was only average; playing the track in Dark Side of the Moon where someone runs across the stage from left to right, the foot and breathing sounds were excellent in the left, but as they moved towards the center they got more and more fuzzy and out of focus and towards excellence again when gone to the right side.
i did a new calibration using this new knowledge and got excellent results right away; something i would have never achieved otherwise.