Bit would you believe my experience has been the opposite of yours with the 280's? I wonder if it has anything to do with when they were made? Are yours older or newer? I got mine about 3 years ago and they actually have a bit too much meat in the low end....if you can believe that? Agree on the awesome isolation and also that I can't mix on them at all.
Interesting. We both conclude that we can't mix on them, but for completely opposite reasons. You could be right about a design change; mine are about 8 years old, so maybe the low end was improved in the intervening years.
JonBuoy's absolutely correct about "learning" headphones. The more hours you spend listening to music, especially other peoples' music, on them, the better they'll translate for you. But you can't learn what you can't hear. If a pair of headphones have a very poor response over 6KHz or below 100Hz, for example, they're going to have limited applications.
Still, I do like my Sennheisers a lot. They're comfortable and quiet. I have used them on airplanes and they sound better than Bose "noise-cancelling" headphones that you see so many passengers wearing these days. For less than half the price, too.
Which brings me to my own question for you all:
what under-$500 headphones would you recommend for pleasure listening? Not critical listening for mixing and diagnostic purposes, but just to kick back and be enveloped by nice sound. I've auditioned some Sony headphones that sell for around $500 that sounded quite luscious, but my personal boycott of Sony is still in effect.