Rename to m4r doesn't work for me...
I picked up a 3G yesterday and have read the posts regarding cutting the clip down to <= 30 sec then renaming the file to m4r, then importing it into itunes as a ringtone and syncing it over to the phone.
I did all that and though it shows as a ringtone in itunes, it is not available as a ringtone on the phone. I do not yet have an app to view/manipulate the files system to see if the file actually copied over.
Forgot to mention i am currently syncing on a PC. Plan to fully cross over when I pick up a macbook(pro) sometime next week.