If you're using HFS+ for a filesystem, you're out of luck with PEAR, I think, because of the pear/PEAR file/directory that PHP uses. HFS+ <em>preserves</em> case but does not particularly <em>adhere</em> to case, so at some point there's an issue with there being a 'pear' file and a 'PEAR' directory.
Does anyone know if you can force pear or PEAR to be called something else?
-Rob