>#3 -- SpamSieve is having issues as well (SLOW loading, non-responsive)
Though I had no issues concerning PM after installing Leopard, I experienced the same behavior of SpamSieve. However, looking through the developer's forum, I found the solution: reduce the size of the corpus file. <http://c-command.com/forums/showpost.php?p=3313&postcount=14> "...make it much faster by pruning your corpus. Choose Filter > Show Corpus, sort by Last Used, and delete the words that haven't been used within the last year." Now SpamSieve is starting as fast and responsible as under Tiger. Cheers, Karsten