Ed Taekema of Road Warrior Collaboration has tried to replace his paper Franklin-Covey planner with a PDA.
I have found the palm to be very effective at information management using tools like AvantGo, Acrobat for Palm, JPluck, Franklin Planner for Palm and the palm address manager but have found it to be inadequate as a planning and overall life management tool. For now I am going to go back to using my paper based planner and continue to use the palm to store data that I need close at hand. Perhaps that will produce the best synergy of the two tools.
I don't know that my PDA / Outlook combination would ever be considered a "life management tool," but I don't know that I ever got that far with my Covey planner either. I can do most of the things I need with this combination. I've added a portable keyboard to the PDA, making note-taking much easier for longer events. I've also been using Chapura's KeySuite to sync with Outlook and find it much better than the basic PocketMirror that came with the PDA. I particularly like being able to use more than 15 categories and the notes field breaks the 1500 character limit of the default Palm tools. Now if they would just add Journal synchronization, I would be all set. (They have an earlier product, PocketJournal, but it is limited.)
The one big thing that I have not been able to do is regular planning activities, especially the monthly "what important things need to happen in the next month" session with myself. I am better at the weekly review and look-forward activity, and I think these could be better too. I keep these in a repeating appointment with myself at the beginning of every week. I completely recognize that this has very little to do with the tools and everything to do with me. I've liked the idea of keeping these planning notes within my electronic information cloud, but I need to actually do the planning for this to be helpful.