I believe the BB messenger is for Blackberry-to-Blackberry messages only, since you have to use the person's PIN to add them to your list. it's really nice... my husband and I both have Pearls and we have a running conversation in BB messenger instead of sending tons of text messages while we're bored on our separate bus commutes after work. :)
no subject
the things I love are:
Opera Mini
Poynt
UberTwitter (if you tweet)
Flickr Uploader (if you use them)
WeatherEye or BB Push Weather Info - I've noticed the latter is more accurate.