I've burned in my igrado's now for over 60 hours with music.
I'm really taken aback at how much the sound signature has changed. They've gone from having very noticeably boosted highs to a much more mellow sound. They sound like a warmer, more detailed version of the portapros, including a signature bass kick and oomph.
The igrado's were just too hot out of the box, but I almost miss those over-emphasized higher frequencies (not really :)).
Anyway, at least with the igrado's, burn in is a very real, objective phenomenon. This is the first pair of headphones which has changed significantly after burn-in.
The igrado's are just ok for comfort, but are tolerable for shorter listening sessions. I will most likely keep them.