I have a confession to make: I use Microsoft Outlook.
Not at home, but in the office. I know many people are stuck with Microsoft Outlook because their company uses an Exchange server, but that is not the case with me; I am free to choose. I use Microsoft Outlook because it allows me to do some things I can't accomplish with other tools, even though there are many things I don't like about Outlook.
The main feature that has become indispensable for my is the fact that I can adjust any view to my needs. I have a huge list of contacts, which I have grouped in two levels (country and company). That way I can quickly find contact information. Unfortunately, when I select a contact from a new message window, all I have is a huge flat list of contacts. Another feature I use frequently us the ability to add fields to items. All my task fields have an additional field called 'project', where I put the name of the project this task belongs to. If I group my tasks by project I have a good overview off all pending items per project.
The features mentioned above are essential for my functioning in the office. Some other features are simply handy to have. For example, conditional formatting allows me to change the view of an item, so that I can see quickly which items have to be processed today or in the coming week, and which items are in progress.
As bloated as Outlook may be (partly fixed by some add-ons), I haven't found a better PIM.