I'd say it really depends on what you want to use your BB for. I use Jivetalk, Google Sync to sync my calendar. I also have a bunch of pictures and videos for when I'm bored. I have a pretty updated autotext memory base since I'm kind of lazy sometimes (especially for writing my own e-mail address, tlphone number, web albums, websites, etc.). Facebook's a fun application. SMS2MAIL is a must have, it automatically e-mails a copy of all incomming SMS's to an e-mail address of your choice! Great way to never have to worry about deleting ;). Hope this helps
Also, familiarize yourself with the keyboard shortcuts, save a lot of time