first of all -i'd like to know exactly what debussy was attempting to express. i see the words 'les tierces alternees' at the very end of the piece. what do those words mean. the three alternates? what is he referring to? staves?
at a first viewing - i would say that debussy is attempting to get the student to sightread notes faster and make mental changes for staves at lightening speed. not to be 'set' on one group or placement at the piano. and - to listen for the types of thirds that one is playing.
debussy was very revolutionary in that he is not making it a particularly difficult piece to play technically - but rather musically. to listen for things that make things 'musical.' also, i think debussy is making a point about fingering. to find the most comfortable one - because no rules exist for this etude particularly - do they? i heard that debussy didn't finger his music.
in terms of musical value - i really couldn't answer that one because i've not attempted to play it and my printer has run out of paper. in just looking at the etude - it makes me think that he has something in mind regarding how playing the piano 'looks' to other people. can you imagine someone playing this piece really fast. it might make you laugh. debussy visualized not just the music itself - but people playing it.