I used to do a lot of taping of live events (once a week at least for several years), and I started out with a minidisc unit. It didn't take me long to become frustrated with the lossy compression scheme, even though I do think that the ATRAC is far superior to MP3. After a few comparisons between my minidisc recordings and the master DAT recordings from the deck that I had patched out of (meaning the identical signal was recorded on both devices) it became obvious that the minidisc recordings were clearly inferior to the uncompressed versions. They still sounded good if you didn't have the DAT master to compare against, but when actually put to the test it was very easy to pick the compressed minidisc version.
So, at that time I ditched the minidisc and picked up a DAT deck. Much better recording quality, even my wife could tell the difference. However, DAT has to be one of the fussiest, problem-prone recording formats I have ever used. So now that all these hard-drive recorders are hitting the market I sold my DAT gear and am waiting to pick up my first hard-drive recorder.
The Hi-MD seems like a winner, that wasn't available when I was running minidiscs. However, the 90-minute limit per disc is a bit short for me, I had grown accustomed to the 3-hour DAT tapes! Many people I know have switched to the Nomad Jukebox 3, which has a line-in (but the A-D is very poor) and an optical input as well, allowing the use of an external A-D converter. It can record uncompressed .wavs and can hold a lot of music. I think they have discontinued the model though. Now I am seeing a few new hard drive recorders hitting the market, and I suspect they will become reasonably priced before too long. The Edirol unit looks promising, but I think Sound Devices has a couple of really nice units either out now or coming out soon. I hear one of them referred to as the SD722 but I have yet to see one in person.
I will be interested to hear how you like the Hi-MD unit. If you need any tips/advice I am happy to share my experience, I have certainly taped my share of shows, both openly and stealth-recording!