If there is one tool I use more than Visual Studio it is certainly Outlook, I have been an Outlook fan since Outlook 2003 (before that it was just ok) and have not looked back since. I decided recently to give the Office 12 Beta a try and while I tend to shy away from beta 1 stuff for actual usage I was quite pleased with the relative stability. Now after having spent a few weeks mainly in Outlook and Word I have to say that this has got to be the best Office release by a long shot.
I know people get into arguments about whether there is some killer 'must have' feature and whether the new features justify the upgrade cost and on the surface I could not name just one that makes it worth while but this thing is truly a starting to shine as I dig more.
If you have the opportunity I really suggest playing with it for a bit, it is going to knock your socks off in a lot of respects.