I find the blackberry to be valuable for the following:
-Sending/Receiving email when on the go
-Looking briefly at task lists when on the go
-Serve as a good reminder of appts via alarm
-Keeping calendar up to date when on the go
It has not worked for me to:
-Capture new tasks
-Use as a primary task list
I still value a print out to paper lists!
Your mileage may vary...