Some things I've noticed- while it may be obvious to old bbm'ers, for me and others, it's new. I'm on Android.
There are 3 ways to chat, personal (one on one), multi person, which is done by adding people your personal conversation, and group chat. All three have different features of what you can do.
Personal, among other features, you can also ping and send videos, although sending vids is not straight forward. You can not send a vid from within the app. You must go to gallery and click share with bbm.
Multi person still allows you to ping, but disallows video sending.
Group chat allows neither video sending nor ping.