Useful for what, the clip series are music players with fm reception thrown in. You get to record via a built in microphone useful for occasional use or to take notes. You can even record off the fm radio, something you might like when you can't listen live to your favorite talk show. You can even Rockbox the thing to add some alternate functionality. This is readily done without dismantling the unit.
But it is basically designed to play pre-recorded music. For long recordings, such as lectures you are much better off picking up a dedicated unit, preferably digital that will do a much better job with better control of playback etc. For field recording you either live with what is built in or acquire equipment designed for that purpose. The vast majority of users would only consider cracking the case open to fix a broken unit.