Compared the Oppo BDP-83 with the BDP-83SE upgrade. It should be said that there was only 1 hour of burn-in on the newer one, and at least a hundred -- if not hundreds -- on the old one.
It's worth the upgrade just for the better stereo separation alone, especially with headphone listening, clearly, audibly better. Bass is just a touch more on the old one, but can only be heard on the best of headphones, and it's close enough that I'll just get used to it. Top end is nice and extended. Old one might just be a little smoother, and at the same time just a touch punchier, but only one of us could hear the latter difference (I.E. not me). I suspect the smoothness factor will go away with more burn-in, but will never know, since the other is being shipped off as soon as the RMA is received. I might ask my boss to bring his (old one) in after a month or so to see if we can tell the same differences.