Like all Sony things, the MD was discontinued when it reached its best usability (supporting .wav format and usb transfer without an horribly bugged drm manager inbetween).
I had — still have — an MD walkman, and what i love about the format is that in many aspects it felt still like cassette tape:
it has a limited capacity of a few hours, so you can group tracks and albums and remember them being in that particular disc; ripping CDs was slow and difficult (SonicStage ), so much of the time i just recorded from line in; i always had lots of partly labeled discs and homemade compilations around my bag;
yet the tape did not break (obviously), there was no wow when weather got too hot.
It worked wonders to make concealed recordings of concerts.
Only problem is there was no one to trade MD compilations with ^^'
I would love to engage in some sort of MD-mail art. Maybe one MD could circulate, where each participant would do something on it (add a track?), and two years later someone has the master for a great compilation.