Does somebody know where I can find the piano sheet music for the song
"Why or Why Not" from Higurashi no Naku Koro Ni. If not could somebody please transcribe it? The mp3 can be found at Gendou.com

Actually, i was wondering the very same thing...
seeing there no reply for 2 weeks, can i assume that no one's already transcribed it, or is transcribing it?

Well, I have been looking for the same thing for a long time since hearing that piano bit in the preview of each episode...
I tried to transcribe it a year ago but it didn't sound right, so i gave up. (Well, i thought maybe it just isn't something to be played by 2 hands. and i was even worse at transcribing at that time.)
nonetheless the intro and ending only version is on my website http://sperion.web.fc2.com

Awesome. Sounds good man. Thanks :)