I just listened to Ondine, played it myself recently. Beautifully played, a very refreshing interpretation, and good balance between accompaniement and melody - one of the real difficulties with this piece, I think.
As I wrote in my own "Ondine thread" (it's somewhere in the Audition room), my former teacher studied with Vlado Perlemuter, who studied Ravels complete works with the composer. Ravel was very careful about details in his works and could work with Perlemuter on a single bar in a simple valse for an hour, making him play it over and over again until he got it right. If there's anything I think you could work on more (because you have all the technique and colour you need for the piece), it is to take a closer look at what's written in the score and avoid adding too much to this. This might sound boring for an interpreter, but why not be an open window for the music on the score? Remember what the composer said: "One should not interpret my music, one should realize it." One last thing, which I also wrote about when I posted my "Ondine" recording, is that I prefer a somewhat slower tempo where all accompaniement figures can be heard clearly and evenly - almost the clarity you need for a Mozart sonata. Try to imitate how a harpist would play these arpeggios.
Well, I shouldn't say too much because you play this far far better than I do! Any advice for practicing the double-note passage before the climax? I've always found it really hard to pull off, started practicing Chopins op 25 no 6 to improve thirds, hoping it could help.
Topic: Ravel: Ondine & Scarbo from "Gaspard de la Nuit"