I'm aware of the huge leap from Raindrop to the etude but then agian I don't find any of the other piece challanging at all. I already know the first 3 bars of the Ab etude up to speed but I've noticed it becomes rather challing after a while... Oh well.
Wow . . . not challenging at all - I envy you! Try the A minor Winter Wind Op.25 No.11, or the Thirds Op.25 No.6, or No.1, 2, 4 from Op.10. Try also the Sonatas, Ballades and Scherzos. Or Preludes Op.28 No.8, 10, 16, 18, 19, 24 ?
I think you should play works of Liszt first before attempting the Op25 etude. Liszt, after all, helped Chopin compose the works. Why dont you play "Un Sospiro"- it is similar in tone to the Aflat Etude, and will get you ready for the arpeggios that wreak hell on many students..donjuan