I'm not sure why Wombat feels so strongly about the use of the word average, when not referring to the mathematical definition. Here is Webster's definition:
1: equaling an arithmetic mean2 a: being about midway between extremes <a man of average height>b: not out of the ordinary : common <the average person>
— av·er·age·ly adverb
— av·er·age·ness noun
The definition I highlighted is the one Cheapy was using for his review scale, which is completely appropriate.