Listening to the M50 again on my rotation is like falling in love all over again. Portable, easy to drive, awfully fun sounding and a non-picky performer. The fact that it's a pretty common entry choice into headphilia doesn't give it much esoteric appeal, but there's a reason why it's so readily recommendable.
That said, I can see where the treble complaints are coming from, and it seems to be an effect of the v-shaped curve. Cranking the volume to bring the mids up causes it to sound noticably hot.