It all depends on what you need your BB for.. Also, we Europeans exclude most navigation apps, such as Poynt or WHERE since they dont support our countries yet.
Therefore, just after a new OS installation, i install the following:
BBOS Alert (Thanks BBOS
BerryWeather 1.6 (Used to install it but noticed it DRAINS my phone's memory)
Weather Channel App (New updated - launched a couple of weeks ago)
I also got SearchIt, Process Viewer, Griddler, RIM Twitter App, SocialScope, but none of them is often used