If you -like me- were suffering from being unable to load big attachments through ext/imap because of PHPs memory limit, the new imap_savebody() function should be what you were looking for. It adds the ability to save any section (full mail, too) of a mail message to a file or stream.
Adding it implied a non-trivial change to ext/imap, so if you encounter any new problems -with f.e. imap_fetchbody()- speak up ASAP, please! ;)