Goomz: Good poll question. The quick answer is "yes."

More specifically, I have been known to kick the center channel volume up a notch if I feel the dialog is getting buried in the soundtrack. Apart from that, when listening to two-channel sources, I may adjust the front L/R speakers +/- a decibel or two if I feel the center image (such as a vocal) is leaning too much to the right or left.

Lastly, when I calibrated my subwoofer with the SMS-1, the default volume was 35dB. I have found that a bit too much for most of the stuff I listen to, so I've backed that down 5dB.

It's funny when you do this though; you can wind up dialing in your system to a particular movie or album, forget to set things back, and then before you know it, your calibrations are out of whack!