I have both. They serve different functions. My PDA keeps my schedule, with alarms for everything, repeated reminders, etc. and my phone book--as well as dictionaries, books, games, note pads. And it's little, and easy to consult, without having to boot it up every time I want to check something. (ie. Westlaw password..) I also read books on the subway--my Palm is a lot easier to juggle than a book, and I've got about 30 books loaded on it.
I wouldn't give up my Palm, my laptop, OR cellphone.