Xobni is an excellent add-on for Microsoft Outlook and has definitely simplified email management for me. Even Bill Gates fell in love with this application and referred it as the next generation of social networking.
(Microsoft did try to acquire Xobni and it failed due to various reasons)
The following video highlights the unique features in Xobni
I have been using it for quite some weeks now and it has negligible effect on Outlook’s performance. Try Xobni !