I've got the Sony MZ-R900 portable recorder/player. And I must say it's great! Cheap media, long recording time if you reduce quality a bit, and it's tiny! Plus a bettery life of several days non stop playing. Also for all the "modders" out there it's another gizmo to improve. So far I've made a tiny mic, an optical output from my soundcard and an interface to my computer making automatic titling a possibility.
The only downside to MD in my book, is the real time recording. So on max compression you can record about 5 hours of music, but this takes 5 hours to do.. Some newer players have higher speed recording, but I haven't used one of those yet. Oh, and I'll be using it a lot doing interviews for my masters degree!