I have had lots and lots of contact management software, none of which ultimately served my purpose: to really really quickly grab information and get in on my calendar, without having to tab through too many fields and options and views.
MrDiary givers me one view, very fast and intuitive navigation and almosts all of the information is free form, which is perfect for me. I have it on my mac and on 2 PC's and its going onto another PC and another Mac...
On PC notebook sits next to a phone where it serves as a phone book and instant calendar... again, it being one frame and free form, I can get information into it really quickly. If I need to clean anything up, I can do it at my leisure.
The diary entries serve as "to do" and I things I've done and I can check them off when I'm done: they don't carry forward, and that's cool too.
There are things that can be improved, but if it never changed, it would be fine. Any features that changed the one view paradigm? I wouldn't use them.