I have been using digital organizers for about 10 years now. I started with Casio series. It was useful for me to keep my contacts / telephone numbers of all my clients. meetings etc.
I purchased a Pocket PC three years ago, ipaq 3630, other than my personal contacts, it helped me to sync my favorite websites and sync my emails with the desktop. I recently changed to ipaq 5450. It is a wireless PocketPC and I am connected to the internet all the time, I can chat with my friends, get e-mails instantly. And yes, it still can maintain my contacts / appointments etc.