BlackBerry Messenger will not be available as a stand alone app on the BlackBerry PlayBook on launch, but is available through BlackBerry Bridge.
“A software update for BBM functionality is expected to be available within a few weeks, and customers will be able to download the software update over-the-air.” – RIM
A majority of app functionality for the PlayBook will be available in the next few weeks as more apps and upgrades are made available.