natural/reverse scrolling usability studies

I am wondering whether there are any usability studies out there regarding natural vs. reverse (traditional) scrolling. I tried to google the matter a bit and it seems natural scrolling took off with some Mac OS version - but remains controversial even in the Mac community.

I generally find using a trackpad clumsy - mainly with regards to scrolling. I have, however, only really used reverse scrolling. My issues are only compounded by natural scrolling, but I am wondering whether it might end up being a better experience if I invested the time needed to get used to it.

I guess Apple must have had some intelligent reason for imposing a standard that needs so much getting used to on the part of their users. IS there any evidence that natural scrolling is a switch worth making?