I was going to jump on the M50X since its 100 bucks no tax to CA peeps. Then I remembered, I have an M50 which I have not use much lol. I use to take it as a portable but the coiled cable on mine was too much for portability. The shorter cable that the M50X comes with is great, well the shortest of the cables it comes with of course.
But since now I use my SoundMagic ES18S and Sennhesier Momentum Over On Ears on the go, kind of seems pointles having another portable...........for now.
M50X offeres better sound isolation though compared the the Momentum and the bass presence is better in the M50X as well but I prefer the Momentum as an all around headphones, though now that the 2.0s came out, I would like to get them, simply because they collapse down for more portability and the pads are slightly bigger and deeper.
In the end, everyone should own an M50, just like everyone should own a Creative Aurvana (I dont own one lol).