I was really disappointed to read about Xobni. Bringing Gmail features to Outlook- and letting you 'pivot' your email by who it is from / to. I am disappointed because I have a great idea for an inbox assistant that I am conceptualizing, and this thing looks much better, if not really on the same track. The good side of it is that I will get a better sense of the market for Outlook plugins from watching their progress.
My idea is a little more focused on another aspect of email- the doing side of things, while Xobni is more on the analytical side. I still really want to try it, even though a few of the details are far from clear at this point...
I've also been checking out the trial for Sandy. It's another email type tool, except it's more of a command line using email. You send Sandy an email and she either updates your calendar, todos, sends a reminder or just remembers it. With the API support, you could think of it as a mail in interface to all of the tools you already use. I really wanted to like it, but it's not quite what I thought it was going to be.
Here's what my tool is going to do- help you get through your email faster and more effectively. I've been on the verge of declaring email bankruptcy a couple of times in the past months and I need this tool to stay at inbox zero (see below video for more on that).