Me & My husband use it all day long!!
We have different schedules, so throughout the day we are constantly BBMing each other. It it great because we dont have to waste our texts that could get pricey with how we are.
Also, we know when the person has or hasnt recieved the message, or if it was even delivered to the phone. You can send pictures back and forth quickly.
I actually had three gens of Blackberry phones before I even tryed using the BBM, now I'm hooked!