One thing I noted, the sp2 release seems to have somewhat uncoordinated documentation. Even the page which says it has the "most up-to-date" documentation on Exchange 2003, the technical library page at http://www.microsoft.com/technet/prodtechnol/exchange/2003/library/default.mspx , does not have any mention of anything newer than the sp1 release notes at present.
Anyway, the purpose of this comment is to say that using some direct examples from the custom weighting file in the release notes doesn't seem to work in my testing. I'm not sure if it's something in my environment or not, but I had my custom weighting file suddenly stop working (none of the entries were having any influence) and seem to have narrowed it down to whenever I have a text entry of 6 characters or less, the entire file's custom weights are no longer used, and no event log errors are logged. As soon as I remove any 6 character or less text entries, the file works again. The file is still being read by the process (confirmed by auditing) but there are no errors generated...