What version of the M50 did you have? I had the older version and the highs didn't even remotely bother me. Supposedly the newer white box versions have even more treble and less bass.
I only tried the newer M50 for amount 20 minutes and couldn't believe how much more treble they had. I didn't get a chance to burn them in though.
There might just be variations between pairs due to updates.
Still got mine, although they rarely see the light of day. Mine are the ones with the little white sticker under the left pad stating #1032.