This thread has turned into a very interesting discussion. Thanks everyone.
For my .02, I am of this mind that when it comes to Mastering.......when you apply a Mastering tool of any sort (Ozone, Har Bal, Waves, etc), if you hear a radical difference in sound when you apply something,
you have a problem in the mix. I agree with what's been said by the experts that any mastering tool is to apply subtle, final sheen. Plus, what sounds good is not not necessarily sonically correct.....keep it clean and tight through mixdown, apply subtle Mastering effect, and your track will stand tall forever, on any system. Sometimes, in the process of using things to make something sound good, we create sonic nightmares.
I truly believe the best recordings are kept as simple as possible.....light on effects and EQ, recorded correctly with alternates (so you have choices at mixdown).....so that when you are mixing down, you are dealing with clean signals. Everything in a mix clamours for space and the muddier each element is, the thicker the mud they create when they come together. In sonic context, less is truly more. And I do not believe there are magic bullets.
Again, just my .02. Carry on