I have the MZ-R30
It's pretty tough, somehow it got dropped really hard and got a dent and still works fine. See pic.
I got it way back when I had dough. The old days of the economy on speed. Anyway, it's not intuitive. Very easy to record over prior tracks. Gotta use the find end button. Nice rechargeable batt included. Still recharges nice after 4 years or so. I just don't get to use it much, no built in mic, all mini jacks, ok for live recording in mono, you get a lot of time out of the regular, cheapo MD's. Compressed audio but not too bad sounding.
One bad thing, it has a lot of internal disk noise that gets recorded even with the external mic that is sold specifically for the unit. Cheap clip too, it broke on second use. That little stereo mic goes for $75 U.S. I think i paid $300 for MD walkman on sale at Wiz in NY....