If it helps, a quick way to teach the filters, if like me you file your good emails in a multitude of different folders...
Firstly get rid of all your current Spam...
Highlight your 'Email' folder (within which are hopefully all your filing folders)
Perform an advanced find, on current folder ('Email'), check 'include subfoldrs' and find '@' in the From field.
Entourage will puff and wheeze a little, but will eventually generate a search list of ALL your emails (assuming each From address contains an '@'!)
Highlight one entry in the search results, under the Edit menu select 'Select All' and now select the 'Mark as NOT junk' script.
Hopefully in the time it takes to drink 2 cups of coffee, you've taught the system something worthwhile...
Thus far, the system has correctly identified 86 items of spam, failed to spot 3 spam messages, and hasn't selected anything I wouldn't want it to have selected!
All in all, a worthwhile addition to my Entourage routine; I've put the app in my log in items and marked it invisible; my final rule is to run the Check For Junk script, so it all seems to take reasonable care of itself. Now if only someone could speed up the processing of scripts!
One final point... when I installed, my Entourage didn't include a Junk folder (which I might have inadvertantly deleted, I can't be sure). Naturally the scripts didn't much appreciate this! So, I created my own, OUTSIDE of the main 'Email' folder (so allow the routine above to function correctly), and so far, so good!
Hope it helps someone.