My number one need for a contact manager/calendar is that it be fast, simple, really really easy to use... want to get to a date for some notes really fast, find a contact, make some notes, add a contact....
I don't need birthdays, reminders, and tons of fields complicate things. Just the essentials, and free form is what I need and what Mr diary does.
Mr. Diary is the best I've used. What's more, the author is REALLY fast at evaluating and responding to suggestions.
I use it on the Mac and on the PC.