Apparently there is a major bug that will cause the entire contents of your hard-disk to be dumped on to the internet for everyone to see. So if your are this guy: http://www.geekzone.co.nz/forums.asp?forumid=50&topicid=185844 then don't do the upgrade!! lol

But if you don't wear a tinfoil hat, then in my experience Outlook retains all it's settings just fine. Just uninstall old version, reboot, reinstall new version, open Outlook.