I like three features the best, first the search capabilities are very useful I can find stuff easier. Second, organization tools, it's very useful, specially the attachments section, where it will show all attachment in one place. And finally, the analytics provided, is nice to see this information, such as emails in and out for specific person.
Another nice feature regarding searching, is the ability to specify advance search settings, such as including as many search fields as needed, such as From, To, Has Attachments, CC'd, All, With, Date, Body, Subject, etc.
Well, this product seems to be discontinued, so latest version I found didn't work that well with latest version of Outlook. For instance, the panels doesn't seem to aligned very well.
Most importantly, the search problem. It's hard to find emails, attachments and specific email threads when you accumulate thousands of emails. So, adding better search capabilities solves this problem.