These cans definitely do burn-in when time goes on. And I know it's not my brain, since yesterday they were quite harsh sounding on a specific 320 kbps mp3 recording, but since today that harshness is almost COMPLETELY gone.
And the artifical sound has completely gone away. The CAL is still clearer sounding overall, but one some songs the clarity of the FSP is REALLY impressive, even better than the CAL, but not in an artificial way.
I also think that the FSP sounds just SLIGHTY more realistic than the CAL. They have almost the same realistic tone, except the FSP sounds better with guitars, pianos and drums.
It just keeps getting better and better! lol