I just got mine today, as a matter of fact.
So far, it's pretty neat. I am a MD partisan, though. I haven't had time to play with all the features yet, but I like what I see so far. It has both mic-in and optical line-in inputs for recording. I assume that most of the people interested in this will be into it for the ability to record in linear PCM audio. The NetMD functions work as one might expect. It lacks an optical line-out, but, I am not so sure how awful that is on this one, unless you want to run the MD signal through other components. In that case, I'd recommend the new Onkyo Hi-MD deck (available at Audiocubes). The RH10 is powered by a wall wart, internal gumstick, or screw-on battery pack.
I think this one is infinitely better suited to recording than a portable music player. The EL display lets the taper see what is going on with the levels and navigate menus without any real problem. The screw-on battery pack really makes the thing limited only by the number of AA's one can find. This would also make a good lecture, meeting, garage band, sermon, etc. recorder. It is small, unobtrusive, and light. Unfortunately, I see MD becoming the new, and longer-lived, DAT. Flash and HDD players have a stranglehold on the digital music game. However, they are not recording audio with any great ability yet. Sony's neverending series of MD blunders has pretty well put the format in a position to be the semi-professional recording medium of choice. This new RH10 is a good recording platform, now that the titling error has been corrected.
Playback is nice. I always preferred, and still do, the sound of the MD DAC to the iPod. The MD players sound a bit more "neutral," but that is only IMO. The large, clear display has all the information one could want about the track. The menus are easy to navigate. The buttons are smallish, but I get the impression that they want you to use the included remote more than the buttons on the case. It is a combination of metal and plastic. It isn't as tank-like as the earlier models, but I don't fear its destruction in normal use. There are those still rather attached to the NH-series (which was, as I recall, 1st-gen Hi-MD)
PM me with any specific questions.