There is at least one case I know of where you don't really have a choice about using PATH_INFO.

If you want to download a file on the fly to be read by Excel, with IE 4 and some versions of Excel it will break horribly if IE knows that it is dealing with a CGI script. The only workaround I know of is to hide the fact of a CGI script using PATH_INFO. (The actual bug is that the path to the temp file is split on spaces before being passed to Excel. Since that path often has "Temporary Internet Files" in it, this results in Excel not finding the temporary file with your data.)