Just recently, a friend of another keyboardist I know, recorded a live session for us(without asking, I may add), and later in the day, played it back. It sounded reasonably alright, but nothing that compared to a well mastered recording session. I think they are OK, for listening to a general sound, or if you're working out licks, or even composing, which we were...but when it's all said and done, they just don't match the quality of a serious recording session....BUT, they sure are handy!

By the way, I've also found it VERY useful NOT to listen back to what you've recorded, till the next day...or at least a few hours after...the reason is, musicians are still in an 'active mind', and NOTHING will sound right, as far as what you played. If you give it a time span, to let your mind slow down from playing, you can listen to it more objectively, in a 'passive mind'...which most all people listen to, anyway....You'll find yourself overly critical, imagining other licks you could have played(because you're still in 'playing mode'), and won't settle down to listen to what is actually THERE!
Another word of caution...when you listen back, at anytime, don't dismiss simple mistakes, and get accustomed to listening to it 'wrong'...Always work toward perfection, in every tone, phrasing, expression and virtuosity(the ability to play and convey with feeling), and of course, the notes. We used to have an expression in the studio..."The Feeling is GREAT!!!..but the notes are all wrong!!"

Again, with a good recording session, you want to hear every nano-second, and make it seamless...your listening audience, may not be as forgiving, as you might be, making excuses, and glossing over, thinking, 'Well, it's OK, it was close enough'!..(wrong!!)..and if you can't get it exactly right, PRACTICE MORE!
...and for those practice sessions, those little recorders come in pretty nice.

Regards to ALL serious musicians out there....making things better may rest on our shoulders!!

GfS