M-Audio Flash Tracker!!! This is the one!!!
I'm also looking for a similiar such miniDisc replacement, and this forthcoming M-Audio device looks like the best bet so far! Good specs, not so expensive ($399 - a little higher than i'd like, but not bad). Except it's not shipping yet.
I've been using an IRiver H-120 20 GB mp3 player / recorder that works pretty well, and it's got digital inputs and outputs, in addition to a Mic In, Line In, and a built in Mic. You can make good recordings with an external microphone, and it records in many mp3 resolutions, as well as uncompressed .WAVE files. Only trouble is that it doesn't have level or clip indicators, nor is it easy to adjust the input gain while recording.
The trouble with all the recording features on the MP3 players is that they seem to be added as an afterthought - they're not as complete or accessible as the recording controls on a MD player, or something like the R-1 mentioned above.
I'm excited about this M-Audio device - seems like what everyone's been looking for.