>These things seem great--but is mp3 really equivalent to CD sound quality?
Yes -- or better (or worse) based on sampling rate and quality of input (i.e. audio source, gear, audio-digital conversion etc.)
One quick note regarding the recording of live music: I haven't seen anything that records directly into MP3 format. This site lists an upcoming product that will do that however:
The other item I saw records, but only in .wav format so you won't get any compression. Depending on what sampling rate it records at, 6GB will get eaten up pretty fast. Someone else can do the exact math, but I bet it's along the lines of 40 - 50 MB for a CD quality, stereo recording of 3 - 4 minutes.
I'll keep my MiniDisc for now (convenience/price/performance ratio), but could see myself going to an MP3 recorder eventually.