Instruct: Classify Amazon reviews into positive or negative sentiment
Query: SpamKiller 5 is not an upgrade

SpamKiller 4 is much better. I promptly reinstalled it after trying 5.0. SpamKiller 5 doesn't run in the system tray and doesn't notify you when your receive new email. The interface looks nicer but is slower and less functional. Recommend getting SpamKiller 4 while it's still available. (Update: One person told me they liked Norton AntiSpam, but all the reviews say it's buggy and slow, so I wouldn't recommend it over SpamKiller 4.)