Cam, you mention only the "calibrate" function of Audyssey, which is just part of the story. Yes, you should use Audyssey to calibrate speaker levels and distance delays; the result using the internal meter and processing is likely to be at least as accurate as a manual calibration with the aid of an external SPL meter. Any difference observed when "checking" with the separate meter is just as likely to be due to user error in reading the meter.
Besides calibration, the second part of the Audyssey function is room equalization. This is more controversial and should be experimented with as a separate matter from calibration. The majority of professional tests and user reports appear to indicate that results are favorable in partially correcting some of the room effects that affect all speakers.
