I've found that Audyssey does a good enough job that I don't worry about double checking levels and distances. Most cheaper ratshack meters aren't going to be accurate enough through the entire frequency range from what I understand.
Note #2) Audyssey uses the distances to make timing adjustments and won't always match up with what you measure with a ruler. It's more about milliseconds than it is feet n inches. Especially with subwoofers, so I wouldn't change those either, even if they're off. For instance, I have a minidsp on my subwoofers so Audyssey adds a couple of feet to make up for the additional time required for processing.