I took my PDA to WDW the past 2 years and I will be using it again later this month, here is how I used my PDA for both planning and at WDW:
In Memo Pad I created a category call WDW, where I listed my PS, attractions to see, driving directions,
DVC information and my trip report.
In Date Book I manage my daily schedule and the attractions I visited, using Note to write a quick summary then transfer it back to trip report after I returned to the resort.
AvantGo channels: INTERCOT's Disney World News. Orlando Park Hours, which gives you 1 or 2 months of operating hours for all WDW parks as well as USF, IOA & Seaworld. Menus From Around The World.
Doc-To-Go is a 3rd party software that came with my Sony Clie, I created an Expense Report in Sheet-To-Go, this way I can keep track of expenses during my trip (although I prefer the Expense program that came standard with my old Vsor Dx), In Word-To-Go I copy & paste many informations: Hidden Mickeys location, AP FAQ, BoardWalk Villas FAQ, resorts phone and fax numbers. I will try to write a trip report using this program for my next trip.
PG Pocket is standard software came with my Clie, I loaded pictures from previous WDW trips, I will add more pictures from my next trip, I can also creat a photo slide show and save it.
Hope above information is helpful, enjoy your new PDA at WDW