I've used PI for two years, first on my Ipaq and now on the MDA, and find it better than Outlook. It is complex and after reading the manual I was amazed at how much functionality they've crammed into a PPC program.
The problem is that after reading it, unless you use these features frequently there is no way you'll remember them all. Even so, its functionality is intuitive enough for me and I'm happy with it.
HL, you can use it for one-handed dialing by enabling the "ABC Tab Bar," which allows you to scroll through the alphabet with the left and right buttons, and up and down the list with the up and down buttons. Outlook works like this too, IIRC. I find it works fine, and to simplify it I have set my most-used contacts to a filter and set the filter as the default. So, instead of a few hundred contacts to scroll through I only have several dozen.
I've put the most-used of this group in Speed Dial, too.