With the latest release of BlackBerry PlayBook OS v18.104.22.1684, I have noticed that I now received BlackBerry App World notifications. As you can see from my screen shot, you will receive an ! in the top upper left corner of the screen. Just tap on it and a notifications pop up appears. From there, if you tap your notification, you are taken directly to the app page so you can update. In my opinion, this was a much needed function.