Interesting comment, Bub. I find the absolute best tool for mixing is listening to a reference CD by a band I like in a similar genre through the studio monitors and comparing it to my mix.
It cuts both ways, too. I was using "Making Promises" by Indigo Girls as a reference for a project I was mixing with similar instrumentation and vocals. When I put "Making Promises" in, I was shocked by how squashed (over-compressed) it seemed compared to my uncompressed mix. I had never noticed that until I was doing an A/B comparison.
I was listening more for EQ and balance than for compression, but was really surrpised how much compression I heard on a folk-pop project with so much reliance on acoustic instruments.
(Or you could listen to Justin Bieber and do the opposite.)