I find that the reminders for anniversaries and appointments work well for me and I don't need much more than that, but others' needs may be different.
I recently started using the principles of Getting Things Done, which actually discourage people from using reminders for tasks as they can just add to the overall stress level. The whole point of GTD is around dealing with busy schedules, which requires a lot of flexibility and task reminders fixed to a particular day and time go against that.
I am using this
BlackBerry GTD app called Viira, it's a pretty good organizational tool so you might want to check it out.
And don't give up on your BlackBerry just yet!