Xobni is pretty cool but...
Xobni (Inbox backward) is a great Outlook add-in that add some cool features that let you find information more easily.
It's still in Beta and I encountered a recurring problem where Outlook would simply not close properly and I had to kill it in Task Manager. Upon restart, it complained that it didn't shut down properly and went to check it's data files so I uninstalled Xobni and I will give it a try when it's more baked.
However, I must say that Derek Hatchard and Joel Semeniuk are using it intensively without problems.