I felt the same way; although, I did try out Immersion anyway and it was cool, but I prefer the NodeXL plugin for excel. It doesn't do Gmail yet, but you can do everything Immersion does and much much more on your local machine without having to hand over account access to a third party:

http://nodexl.codeplex.com/

Here's a write-up I did on it in 2011 analyzing the Science Online Conference tweets and my Facebook friends. You can see it's very robust and extensible:

http://ideonexus.com/2011/01/17/social-network-mapping-fun-w...

Currently, the server-side code is not public. But we might open-source parts of it in the future after adding some more features.