Right. If it sounds great, don't EQ!
I just recorded a song and played it for a friend, asking for constructive criticism. I thought it sounded great.
He pointed out the bass, guitar and vox were all occupying the same sonic space, making it a little muddy.
So next time I listened, I heard exactly what he was talking about.
I had to roll off a very little low end on the guitar and vox, add very slight high end to the vox and physically double the guitar an octave higher to seperate the instruments.
It opened that song up bigtime. Like in the Wizard of Oz turned from b+w to color! lol
So now I realize how important it is to get an unbiased opinion to evaluate mixes.
And use it SPARINGLY to seperate elements of your mix. Like Ron said.
But if your mix sounds good, don't touch it.