Until recently people had "tough" choice to make - in your Outlook either run NewsGator or Outlook COM Add-ins with VSTO support. Both of these did not work together. This is because NewsGator did not support .NET Fx 2.0 which is required by VSTO.
Now .NET Fx 2.0 is supported by NewsGator and the issue seems to be resolved. But I still wonder whether NewsGator could use VSTO loader in the future? Then they will run in their own AppDomain without stepping on the toes of other managed Outlook COM Add-ins.
Thanks to Andrew Coates for keeping an eye on this.