tbh, i'd NEVER go as far as taking this approach, unless i was mixing a very straightforward song, like ac/dc style.....not even then, i suppose.
as far as i am concerned, as a listener rather than a mix engineer, i'm into stuff that manages to grab my attention, yet does not get boring after a few listens....and i'm sure many people will agree with me here.
so, ask yourself, what is it about your favorite records that you've listened to countless times, yet you'll sometimes notice new little things even after so much time? is it the songwriting? certainly.
however, i definitely think that little production extras also play a LARGE role into this whole "keep it interesting" thing. and as far as i am concerned, careful panning IS one of these so important production extras.
it's true that panning most things hard left/right will make you get better separated mixes in less time, but think about it - da vinci didn't do his masterclass paintings in one day, did he? it certainly took him quite some time, and i feel the same about serious mixes. to me it's not a bad thing at all to get your basics sorted out pretty quickly, but once the creative process kicks in (e.g. automation etc) i couldn't ever limit myself to only 3 panning positions, as it would get boring real quick.
think about it, do you limit yourself to only one aux send per track? only one layer of automation for the lead vocal?
once again, it obviously depends on the effect you're shooting for. for maximum impact, you could manage to make decent mixes with only hard panning. most dew scented stuff is like this, for example. however, would that very same approach work for a band like katatonia, or opeth?
listen to the great cold distance, ghost reveries, whatever....there's tons of little things all over the place. and while you might not really notice it unless you're looking for it, it certainly adds to the bigger picture.
and imho, that's what it's about.
