Hmmm.... I'm not trying to pat myself on the back, but being as objective as I can, I still hear a world of difference between my mix and others, mostly in terms of air/space & overall sonic balance.
Having said that - I didn't do anything exceptional to the tracks to obtain it - just judicious EQ, judicious use of compression/gating, along with careful effect selection. The only "production" change was copying the electric gtr parts over to the last chorus and doubling the backgrounds on the chorus bits....
IMO - the problems I heard on most people's mixes in general terms included heavy-handed low-end (seriously - check your monitoring systems - I don't think you're all hearing the low-end properly if you have to put that much on there!) - over EQ'ing, under-EQ'ing - and a common one: serious overuse of effects....
To me - mixing is both science AND art -- the science comes in in getting the sonic balance right and that is more or less a constant relative to all other audio we hear, but the art is in creative use of effects, pulling/pushing mix elements, changes to mix dynamics -- all these things are creative and subjective - dictated by personal preference. Go too far though, and you lose the critical mix balance that makes the mix translate to most people's ears (and sound systems) reasonably well.
PS - (And yes, I was lazy on the de-essing - didn't have the time to commit to this as I would have liked!)