I think for music production and monitoring, the D2000 and even the M50 would be a poor choice. It seems like one would need a more neutral headphone instead. The M50 is closer to being neutral maybe, but not even close to me. Both i'd consider "Fun" headphones.
To my ears the D2000 is far better than the M50 in nearly every way. This is kind of to be expected since it's almost $100 more.
Please note that I had the black boxed M50 with the flap. The new one is supposed to be more bright and has less bass perhaps.
You may find this hard to believe but my D2000 when connected to a desktop amp has better mids than the M50. In comparison I don't find them recessed, which makes no sense because it goes against what everyone says. Maybe 1-2% compared to a neutral headphone, but that's so low to me it's not even worth mentioning. People seem to say they're recessed as if it ruins the D2000. Maybe they made minor changes to the new 2010 D2000's? Doubt it, but it's possible!
The soundstage of the D2000 is also far better than the M50. For being a closed headphone, it has a very good soundstage. It's hard to believe it's closed.
Comfort and build quality is also far better. I'm aware of a couple people having some problems with the D2000, but mine are fine so far. If it wasn't for the weight, they'd be some of the most comfortable headphones i've EVER owned. The k240 Studio come in 2nd place for comfort.
I found the highs on my M50 very rolled off. Even more so than the SRH-840! The white box versions sounded different to me and are more treble heavy then before to my ears.
The bass on my M50 was not very controlled, a bit bloated and boomy. Even without a ton of bass showing up, vocals on my pair were recessed and often slightly hard to hear. On my D2000 they're very easy to hear and I don't find them distant or recessed sounding in any way.
It could all be to synergy. I tried them without an amp once and hated them. Without being properly amped I could see them being described as having bloated bass or recessed mids.
Chances are that if I had the white box M50 my opinion might change, who knows! Remember that despite all my M50 complaints it was still "good" for a $100 headphone, but not great. The D2000 is only worth the upgrade when amped with a receiver or desktop amp. Definitely not worth it for gaming or for use as a studio monitor. They're a good pair with my k601 for when I need lots more bass.