I've had Xobni running on my new work computer since I started in December. It is an Outlook plugin that lets you "find people, email & attachments instantly." Essentially, it is a fast search algorithm for your email. Here are some thoughts about how Xobni fits into my worklife.
If you check their website and some of the hype I've seen reported, there is a social networking aspect and there are some interesting things one can do with statistics. But the thing that seems most important to me is the ability to find stuff that I've seen or written already.
I've been looking at how it fits into my regular flow of work. The screen shot to the right is the basic view you get when viewing email from a contact. At the top, it shows the contact (Rhonda) and how frequently I communicate with her. It extracts her phone number and makes a connection to LinkedIn, if she's in there (including a picture). Then it shows all the other people we're connected with: this is the CC list, sorted by how frequently they occur together. This can be quite useful if I know two people have been in a conversation together, but I can't quite remember the second person's name. As far as I have seen, Xobni doesn't do anything more sophisticated with my social network. Below that, I get a list of email threads, with the subject line, how many messages in the thread and how old it is. I particularly like the last one: a list of files that we have exchanged. I can click to open right from the Xobni toolbar.
The reason I went for Xobni is the ability to find stuff in my mail archives. My gold standard is still an application called Lookout, but that product is long gone (absorbed into Microsoft)*. And I haven't been happy with other desktop search tools in relation to email search (they are great for other stuff).
So, how does it do with search? It's fast, since it has an actively updated index of my email. Until recently, it was missing a major component for me: it didn't have deleted emails in the index, so there was a wide swath of email missing from the results. Overall, though, I find the search and the results display just okay. It uses the same toolbar as above to show the search results and any related mail. There aren't good ways to filter the results by anything other than the search term and "people." I frequently want to get a grid (like Lookout gave me) to help me filter in more dimensions.
And what about those handy statistics? I find them to be more interesting than useful. I can slice my email behavior by a number of dimensions, though it primarily shows me the flow a different time slices: hourly, daily, weekly... In general, I can see that I receive about twice as much mail as I send and that the bulk of that happens during work hours with a small blip after the kids go to bed. If I were really curious, I could also explore mean time to respond (of my contacts to me). This screen is my hourly average received and sent mail.
* Lookout can work with Outlook, and it can be found in various archives online. The original developer posted something about it last year.