i may be completely off on this one, so please, debussy experts just jump in...but, i would be tempted to hold down the first and last note of the arpeggio as long as possible. when i first learnt the piece, i let go of each note and despite foot pedalling, it seemed dry. i can now hear this piece on the organ in my head, with the bottom and top note being the most prominent.
My thoughts exactly! Always felt like I should hold 1st+last notes (lower+higher that is) of the arpeggios.