This is such a nice elegant fix to Safari! The developer's idea for modifying Preferences works so well, I wish he had the time to add Preferences to handle cookies better. Omniweb's current version does this — but it is not yet stable enough to use. Safari has a Preference to "Accept Cookies: Never," but this does not quite do the job.
All that is needed are two tweaks: (1) Always allow domains such as *apple.com; and (2) Always allow and Dump at end of session domains such as *yahoo.com (for mail).
So simple! I'm no programmer, but I cannot imagine how this would entail much more work. Pithhelmet's developer has already done the bulk of it. This fix would certainly beat out external cookie managers and deleting cookies in Safari by hand!