My teacher once told me...."Some pianists can play Islamey, some cannot. If you cannot, don't try to learn it, your wasting time, if you can...good for them"
Islamey is very much the same techncally, all octaves and fast double notes, and repeated notes. If you have that ability then the piece comes easy (not easy but you know what I mean, speed is not that much of an issue). Best advice I can offer anyone doing this piece is to not get depressed learning it, I would wake up some days and go to the piano, and it would fel as if I'd never practiced it the day before. That happens a lot with big stuff like islamey, but remember...if you spent 4 hours on it one day, and go to it the next day and play badly, it will take a lot less time to get it back to where it was the day before, and it will be stronger. Practice it all seperate voices, but using same fingers, do dotted rhythms, slow metronome work, seperate hands, eyes closed, and then build from there. Some of the worst passages are the LH double notes, and the Leaps. The leaps are evil, just bear with it and eventually it will come with ease.