here is my take on pdas: i love them.
i dont ever use my cell phone because my wife uses up all the minutes so i dont get to use it much. and if we ever go over our 2000 minutes a month, its my fault because she uses the first 1990 minutes and i use the last 11...and its my fault for going over.
i have a sony clie from back in the day...like 3 years ago. for me, it does the job. i need something for contacts, scheduling, occasional news (using avantgo), and something to interface with outlook for my emails (i wish gmail had pop access...). im thinking of upgrading to something that has bluetooth and wifi...maybe the ipaq. the sony clamshell is nice, though i think they stopped making it.
for people who are used to working with pdas, its definitely necessary. if youre not used to it though, its probably not worth it.
im not too into the smartpdaphones because the phone itself is too bulky. i do hear good things about the color blackberry. but too bulky for me. and i dont wanna carry my phone around my belt. i need all my sperm to be healthy.